A 53-country review found counts have more than halved in 46 years, and the decline is speeding up.
Levine et al., 2023 · Human Reproduction Update
First-drop preorder
NUMBNUTS Cooling Kit
$69.00
$179.00
at public launch
Wearable cooling for the one part of your body that works best cool.
- Boxer, 2 reusable Chill Inserts, case and guide
- Cools where the heat actually is
- Natural fibre, no plastic on skin
60nights to try it
$65+ships free, worldwide
100%refund before ship
What's inside the kit
Merino-wool natural-fibre boxer with center cooling sleeve, 2 reusable Chill Inserts, insulated carry case, and first-use guide.
How you use it
Freeze an insert, load the center sleeve, wear it through the heat window, rotate the second insert if you need longer. Remove after the session. Never sleep in it, and never put a frozen insert straight on skin.
Why two inserts
One cools while the other heads back to cold, so you are never waiting on the freezer mid-session.
Shipping and delivery
Shipping is free on orders over $65. Below that it is $7.95 in the United States and $14.95 elsewhere, shown before you pay. Estimated shipment begins by September 30, 2026.
Preorder terms
Payment is taken today to reserve first-drop access. Estimated shipment begins by September 30, 2026. You can request cancellation any time before shipment.
What we do and don't claim
NUMBNUTS is a thermal comfort product built around cooling and plastic-free fabric. It is not a medical device and makes no clinical outcome claims.
By the numbers
The research, stated as figures.
Comfort product, not a medical device.
Saunas, hot seats and long sits push the same direction. Production is sensitive above about +1°C.
Sheynkin et al., 2005Sustained heat lowers sperm measures, and the effect generally reverses once you cool down.
Garolla et al., 2013Small trials, not proof, and not results from this product. But cooling is a studied response, not a folk remedy.
SCOP randomised trial protocol, 2012Figures describe published research on heat, cooling and the male body, not results from this product.
Why trust a preorder
No borrowed hype. Here is what is real today.
You are seeing the real build: the center-sleeve design, the materials, the ship timing, and the use limits. Not a dropshipped repackage.
Materials and dwell-time testing finish before first shipment, and results go to the founders list before kits leave.
We are lining up an independent specialist to review the design before launch. Their words will appear here, with their real name. No paid endorsements, no stand-ins.
Coming before shipWhen real coverage lands, it goes here, with the outlet named and linked. Until then, this space stays empty on purpose.
Coming before shipFrom 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