Peer-reviewed studies show sauna and heat exposure raise scrotal temperature and significantly reduce sperm count and motility.
Oxford, Human ReproductionFor men (and couples) trying to conceive
Trying for a baby? Don't cook your count.
Heat lowers your sperm count, and every trying-to-conceive guide says the same thing: keep cool. NUMBNUTS makes it the easiest box to tick. Comes with a 60-night trial.
Backed by published science
First 500 founders
Ships September 2026
Ships Sep 2026Estimated launch shipment
60-night cool-down trialCancel before ship or refund after you try it
Secure checkoutPowered by Shopify
Backed by sciencePublished, cited research
Comfort use onlyNot a medical device
No loose iceDesigned to load cleanly
The science (the honest version)
Heat hurts sperm. Cooling can help.
Your testicles sit outside the body for a reason. Sperm is made best at 2-3°C below core temperature. Here is what the research actually says.
Once the heat lets up, sperm parameters typically recover within about one cycle (~3 months). The effect is not permanent.
Legacy fertilityA systematic review of scrotal-cooling studies found sperm count improved in roughly half to two-thirds of men, with gains in motility and shape.
Scrotal cooling reviewWear it during the sauna, summer, or any hot stretch to keep the heat off.
Run a daily cooling ritual: the wearable, hands-free way to ice your nuts without the ice burn.
We will not overpromise. Experts do not all agree, and cooling is not a treatment for infertility. What we will say is simple: NUMBNUTS makes it easy to keep things cool, on your terms. Not a medical device. Talk to a doctor about fertility concerns.
See it work
The cooling system, in motion.
Freeze the inserts, load the sleeve, go. No loose ice, no towel hack, nothing to hold in place.
Engineered cooling insert
Center under-support sleeve
Discreet under clothing
Sauna and heat
Built for the heat round.
Wear it during the round to cool the one spot the sauna punishes. Not after, when the damage is done.
How it works
Freeze. Slide. Cool. Rotate.
Inserts go in the freezer. The case keeps them cold to the door.
Into the center sleeve, not a side pocket.
Protect through the heat, or run a daily cool-down.
One runs while the other re-freezes. Always cold.
The difference
Cold where the heat actually hits.
It slides into a center sleeve under the front pouch, in the under-support zone, with fabric between the insert and your skin. Not a side pocket. Not loose ice. Exactly where it counts.
Center under-support zone
Moves with you
No direct frozen contact
Heat or daily ritual
Engineered, not improvised
Most cooling fails at the source.
A bag of ice warms in minutes and burns on contact. The Chill Insert is built to do one job well: hold a steady cool, sit right, and never touch bare skin.
A phase-change core holds a steady, even cool across the whole face, instead of ice that shocks cold then warms in minutes.
Engineered to a comfortable cool temperature, so it cools without the ice-burn risk of a frozen block.
Shaped to seat in the center under-support sleeve, so it stays exactly where you load it.
The sleeve keeps the cool surface off bare skin. Controlled cool, not cold shock.
Freeze, use, refreeze. Nothing to throw away, nothing to refill.
Two inserts means one is heading back to cold while the other runs.
Final dwell-time testing is published before shipment. Real numbers, not promises.
Why not just freeze something
A frozen ziplock is not a cooling system.
Men try ice, gel packs, and wet towels. Here is what actually happens once the heat round starts.
NUMBNUTS
Gel / ice pack
Cold towel
Stays put, hands-free, during the round
Yes
No
No
Fabric layer, never bare frozen on skin
Yes
No
Warms fast
Shaped for the center under-support sleeve
Yes
No
No
Travels cold in an insulated case
Yes
Sometimes
No
Rotation so cold lasts the session
2 inserts
No
No
Discreet enough to actually wear
Yes
No
No
What it costs you over time
One kit, reusable for years
Rebuy, they wear out
Free, and it shows
Gym and recovery
Recovery starts cold.
Load a chilled insert after the lift. A daily cool-down, hands-free, straight from your kit bag.
In the bag, in the routine
No ice. No towel hack. Just load the sleeve.
Freeze the inserts, keep them in the insulated case, then slide one into the center cooling sleeve before the sauna, or as your daily cool-down.
Launch kit
The full Cool System in one kit.
One wearable liner, two Chill Inserts, an insulated case, and a first-use guide. Freeze it, carry it, load it, and keep things cool, in the heat or as a daily ritual.
The engineered garment, built around the center under-support cooling sleeve. This is the hero.
One active insert and one ready to rotate.
Gym-bag ready. Discreet. Not a medical-kit look.
Freezer prep, session use, and stop-if-numb limits.
Trying for a baby?
The easy thing he will actually do.
If you are trying together, heat is one of the simplest things to take off the table. The catch: most men will not faff with frozen peas or loose ice packs. NUMBNUTS turns it into a 30-second habit he will actually keep. Freeze, slide, done.
A lot of our early interest comes from partners who found us first. It is easy to give, easy to use, and fully refundable any time before it ships.
Cooling is about protecting from heat. NUMBNUTS is not a medical device and not a treatment for infertility.
The cool-down checkpoint
Cooling, together.
Run clubs, gym floors, recovery sessions. The cool-down is the new ritual, and founders are first in line.
Where we are
You are reserving early. Here is exactly where the kit stands.
No vapourware, no borrowed hype. NUMBNUTS is founder-run, built in the open. Reserve now and you lock the founder price and your place in the first run.
- DoneDesign defined
The wearable liner, center cooling sleeve, and full kit are designed.
- DoneCooling spec set
Phase-change core and skin-safe barrier, tuned to a comfortable cool.
- NowSampling and testing
Supplier samples and dwell-time testing, with results shared before any kit ships.
- NextProduction run
Founder-batch manufacturing once the samples pass.
- TargetShip September 2026
Kits go to founders first, in reserve order.
You do not wait until September to start. Heat is the one fertility lever you can act on today: ease off the long sauna sits and the laptop-on-lap now, and your kit lands to make staying cool effortless, not a daily fight with frozen peas. The moment you join, you are in: founder updates, a say in the final kit, and first to ship. Start today with our free Heat-Protection Protocol →
Why reserve now, months before it ships? Because reserving locks three things that go away once the first 500 founders fill: the founder price ($129, not the $179 public price), your free Chill Insert 2-pack, and a unit in the first run. Founder reservations fund that run, which is how the founder price exists, and you are fully covered: cancel any time before it ships for a full refund, with the 60-night cool-down trial the day it arrives.
Preorder access
$129$179
Launch Kit
A full wearable system: the cooling liner, center sleeve, 2 engineered Chill Inserts, insulated case, and guide. Founder price $129, locked. The public price is $179 at launch.
One time, not a subscription. Reusable for years, so the cost per use keeps dropping. No monthly bill, ever.
- The engineered cooling liner with the center under-support sleeve (the hero)
- 2 engineered phase-change Chill Inserts, tuned to a comfortable cool
- Insulated carry case and first-use guide
- Founders bonus: a free extra Chill Insert 2-pack ($29 value) in your first shipment
- 60-night cool-down trial once it ships, full refund
The Cold Promise
Reserve today and you are fully refundable any time before it ships, for any reason. After it lands, take 60 nights. If you do not love how it feels, full refund.
Use guardrails
No direct frozen contact. No overnight wear. Stop if numb, painful, or irritated. Follow the use guide before every session.
First 500 founders onlyFounder price and the free insert pack hold until the 500 fill. Ships September 2026.
Fully refundable any time before it ships. No risk to lock your founder price today.
Reserve my kit · $129Secure checkoutNo hidden feesTax and shipping shown before you payFree shipping over $75
Secure checkout
Join the Founders List instead
Not a medical device. Not a treatment for infertility. Use only as directed.
Pick your tier
Reserve the kit that fits your routine.
These are founder prices, locked before launch. The Launch Kit is $179 to the public when preorder closes. Most guys start there; daily sauna users grab the extra inserts.
Start here. Liner, center sleeve, 2 engineered cooling inserts, insulated case, and guide.
Reserve · $1294 cooling inserts total, for daily rotation and fewer freezer resets. Best value per insert.
Reserve · $159Two full kits. Split with your training partner, keep one for travel, or gift the second.
Reserve · $239Most founders add this
Keep a spare set always chilled.
An extra 2-pack of engineered Chill Inserts means one set is always cold while the other rotates, for longer sessions and your daily cool-down.
+ $29
Add a spare 2-pack
Reusable for the long run. One-time add-on.
After launch · Refresh Club
The inserts last for life. The liner is what wears.
Your inserts are reusable for the long run, so there is nothing to refill there. The cooling liner lives against heat and sweat every session, so the Refresh Club keeps a fresh one in your rotation.
Every refresh liner ships at the member price.
Every 1, 2, or 3 months. Skip or cancel anytime.
Hygiene-first. Train in a clean liner, never a worn one.
The Refresh Club opens with launch. Founders get first access and keep the member rate.
Founding members
Be one of the first 500.
This is the founding run: the people building this with us, shaping the final kit, and first to get their hands on it. No borrowed hype, no fake reviews. Just early backers and the work in progress.
Founders refer founders: when preorder opens, invite a mate and you both jump the early-access line.
The launch we are building
Cold Club is coming.
Founders get in before the city does. This is the world we are bringing NUMBNUTS into.
From the founder
We built NUMBNUTS because the alternatives were a joke.
Sperm counts have fallen by more than half in fifty years, and heat is one of the few drivers a man can actually do something about. Saunas, hot commutes, a laptop where it should not be. The science has been clear for years. The products were not. Your options were a bag of frozen peas, an ice pack that burns, or nothing.
So we engineered the thing that should already exist: a wearable cooler that sits exactly where the heat does, holds a comfortable cool, and disappears under your clothes. No loose ice. No ice burn. No white-coat theatre. We lead with published research, we say it cools because we can prove that, and we will never claim it cures anything.
You are reserving before the first run ships, so here is our side of the deal. We charge upfront, we tell you the truth about timing, you can cancel before it ships, and you get sixty nights to try it once it lands. We do not buy reviews and we do not fake scarcity. If you have a question, it reaches me, not a bot.
N
Jaspal Rai
Founder, NUMBNUTS
hello@numbnutsclub.com
Proof before hype
Built in the open. Tested before it ships.
No borrowed reviews. Until the first kits land, the proof is the product, the third-party testing, and the founders building this with us.
Materials and dwell-time testing finish before any kit ships, and the COA is shared before kits go out.
The chilled insert sits in the center cooling sleeve. No direct frozen contact, ever.
Testing results, ship timing, and use limits go to the founders list before launch.
Real buyer reviews appear only after founders receive and use the kit.
FAQ
Everything a careful buyer asks before reserving.
Does heat really affect sperm?
Yes. Your testicles work best 2-3°C below core temperature, and peer-reviewed studies show heat from saunas and hot environments raises scrotal temperature and lowers sperm count and motility. The effect is generally reversible once the heat lets up.
Does cooling actually help?
Studies on scrotal cooling link it to improved sperm count, motility, and shape in many men. Experts do not all agree, and it is not a treatment for infertility. NUMBNUTS simply makes staying cool easy. For fertility concerns, talk to your doctor.
Can I use it as a daily cooling ritual?
Yes, that is a core use. Load a chilled insert for a short daily cool-down: the wearable way to cool without loose ice or ice burn. Keep the center sleeve between insert and skin, and follow the time limits in the guide.
Is this a medical device or a fertility treatment?
No. NUMBNUTS is a wearable cooling product for comfort and cooling. It is not a medical device and not a treatment for infertility, and it does not diagnose, treat, cure, or prevent any condition.
Will the inserts touch my skin?
No. The insert slides into the center cooling sleeve, in the under-support zone beneath the front support pouch. Inserts should never be applied directly to skin.
Can't I just use a gel pack or ice?
You can try, but a freezer gel pack or ice freezes too hard (ice-burn risk), is the wrong shape to stay put, and has no fabric layer. The Chill Inserts are phase-change cooling tuned to a steady, comfortable cool, molded to seat in the center sleeve with fabric between insert and skin, and the insulated case keeps a spare ready to rotate. It is an engineered, wearable system, not a loose pack you hold in place.
How long do the inserts stay cold?
Final dwell-time testing appears before shipment. Actual time depends on freezer prep, case time, ambient temperature, fit, and session length.
Do I ever need to replace the inserts?
No. The Chill Inserts are reusable for the long run. Freeze, use, refreeze. The cooling liner is the part that wears with heat and sweat, so the Refresh Club keeps a fresh liner in your rotation after launch.
Can it make me too cold?
The inserts are tuned to a comfortable cool, not frozen solid, and the center sleeve keeps fabric between insert and skin, with time limits and stop-if-numb guidance. Cooling should feel controlled, never painful.
How do I care for it?
Hand-wash the liner. Freeze inserts only. Do not microwave. Follow the first-use guide before each session.
Can I cancel or return it?
Yes. Cancel any time before it ships for a full refund, for any reason. Once it ships, you get a 60-night cool-down trial: try it, and get a full refund if it is not for you.
When does it ship?
Estimated shipment begins by September 30, 2026. Customers will be updated before shipment if timing changes materially.
Reserve the launch kit
Stop cooking your count. $129.
Fully refundable any time before it ships. 60 nights to love it once it lands.
Reserve my kit · $129Secure checkoutNo hidden feesTax and shipping shown before you payFree shipping over $75
Out in the world
See it in the wild.
A look at the NUMBNUTS world. Verified founder reviews land after the first kits ship.