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
Product visualisation. Final details may vary.
01Merino boxer + centre sleeve
02Cooling inserts included
ReusableA routine, not a refill plan
First-drop preorder
NUMBNUTS Cooling Boxer + Inserts
$69.00
Your fertility deserves a place in your daily routine. Sperm health deserves attention. Everyday heat is one habit you can address. Start with one merino boxer and two reusable inserts for targeted cooling.
- 100% merino wool boxer body and centre sleeve
- Natural-rubber waistband. Two reusable cooling inserts.
- Reusable inserts absorb body heat as they soften.
What's included
One 100% merino wool boxer with a centred merino-wool sleeve and natural-rubber waistband, plus two reusable cooling inserts. No case, guide, or extra accessories are bundled into the launch offer.
How you use it
Place a fully solid insert in the merino centre sleeve. Remove after your session; follow the supplied reset and care instructions. Never use directly on skin or while sleeping.
Why two inserts
Two inserts are included. Each is reusable; follow the supplied reset instructions between sessions.
Shipping and delivery
Currently delivering to the UK and US. Orders of US$65 or more, or the local-currency equivalent, qualify for free delivery. Below that, the final delivery charge is shown at checkout before you pay. Target dispatch: 30 September 2026, subject to final production confirmation.
Preorder terms
Payment is taken today to reserve first-drop access. We are targeting dispatch by 30 September 2026, subject to final production confirmation. You can request cancellation any time before fulfilment.
Why heat matters
Sperm production works best below core body temperature. Modern life keeps adding heat. NUMBNUTS is built around one simple response: put targeted cooling exactly where the heat builds up. See the published studies and research numbers below.
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., 2013Twenty infertile men with prior testicular maldescent used nocturnal air cooling for 12 weeks. Sperm concentration and total count increased; controls were retrospective, and this was not a NUMBNUTS study.
Jung et al., 2005 · International Journal of AndrologyFigures 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 orders leave.
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 cooling system built to hold a solid cooling insert at the centre and disappear under your clothes. No loose ice. No white-coat theatre. We lead with the research on heat, then show exactly what the production product proves. 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, and you can cancel for a full refund before fulfilment. After delivery, your first one-boxer/two-insert bundle is covered by our 60-day first-pair guarantee, with no worn return required. 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
