Founder preorders are open. First-drop price $69.00 · Free delivery on qualifying orders · Full refund before ship
Founder release. The first drop.STOP COOKING
STOP COOKING
YOUR COUNT
Your future deserves more than autopilot. One merino boxer. Two reusable inserts. Targeted cooling for the everyday heat worth paying attention to.
Built on peer-reviewed scienceHeat and fabric, challengedFree delivery on qualifying ordersRefundable before ship
5 questions. Results before email.
Merino boxer body + centre sleeveCools where it countsBacked by published researchNo drugs, no hormonesFree delivery on qualifying ordersRefundable before shipMerino boxer body + centre sleeveCools where it countsBacked by published researchNo drugs, no hormonesFree delivery on qualifying ordersRefundable before ship
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In a 14-man study, a polyester scrotal suspensory sling worn day and night for 12 months led to zero sperm in semen. Counts recovered after removal. A specialised sling experiment, not ordinary boxer wear. Read the study.1
Read this before you scroll past
Sperm counts have halved in 50 years. And the fall is speeding up.
A global research signal too big to ignore. Not a diagnosis of you, and not proof of one single cause.
−51.6%Estimated decline in mean sperm concentration, 1973–2018, among men unselected by fertility in a global meta-analysis.
2× fasterThe modelled annual decline was more than twice as fast after 2000 as across the full study period.
223Studies included in the updated global analysis. A population-level warning, not a prediction of your fertility.
You cannot change your genes. You can change the two things you put on the most heat-sensitive part of your body every single day: heat and plastic. See where you stand.
Source: Levine et al., Human Reproduction Update (2023). Population research, not an individual fertility assessment.
Grounded in published, peer-reviewed research•Fertility & Sterility•Human Reproduction•Human Reproduction Update•Asian Journal of Andrology•Reproductive Biology•Toxicological Sciences•
Grounded in published, peer-reviewed research•Fertility & Sterility•Human Reproduction•Human Reproduction Update•Asian Journal of Andrology•Reproductive Biology•Toxicological Sciences•
The problem
Your sperm health deserves more than autopilot.
You cannot choose your genes. You can choose your daily routine. Sperm health deserves the same attention as your diet, sleep and training.
Read the full scienceHeat
Runs the factory too hot
In 29 men, 60 minutes with a laptop on the lap raised scrotal temperature by 2.6–2.8°C, versus 2.1°C in the same posture without it. That study measured temperature, not sperm counts.2
Plastic
Look past the fabric label
Shafik’s small human experiment tested a polyester scrotal sling, not ordinary boxers. A separate dog study compared polyester with cotton, not wool. Neither shows that everyday synthetic underwear causes infertility.1
Sources: Shafik, human sling study (1992); separate dog textile study (1993); Sheynkin et al., laptop temperature study (2005). These studies did not test NUMBNUTS.
Plastic. Sperm health. A reason to pay attention.
You would not sit in a plastic bag.
You would not sit in a plastic bag.
You might be wearing one.
Polyester, nylon and elastane are plastics. Not plastic-like. Plastic. Polyester belongs to the same PET family as drinks bottles. Now researchers are finding microplastics in human reproductive tissue and studying what that means for sperm health.
What the evidence shows. The semen findings are associations, not proof of cause. The skin experiment tested flame-retardant additives, not plastic fibres crossing skin. These studies did not establish underwear as the exposure route or test whether changing underwear improves fertility.
You cannot control every exposure. You can choose the fabric you wear against your skin.
The system
One boxer. Two inserts.
Merino against your skin. Cooling in the centre. Three steps to make it a routine.
01
Insert.
Place a fully solid insert in the merino centre sleeve. Never directly on skin.
02
Cool.
It absorbs body heat as it gradually softens.
03
Reset.
Remove after your session. Follow the supplied reset instructions. Do not sleep in the inserts.
What is inside One system.
One system.
Nothing extra.
The first drop. Everything in the offer, nothing extra.
- One merino boxer, with a centred merino sleeve and natural-rubber waistband.
- Two reusable cooling inserts.
Why it wins
Most boxers do the exact opposite.
| NUMBNUTS | Regular boxers | Loose ice packs | |
|---|---|---|---|
| Cooling-interface material | Merino wool | Varies | n/a |
| Targeted cooling | Built in | No | Cold, but loose |
| Wearable and discreet | Yes | Yes | No |
| Built to reuse | Yes | Yes | Varies by pack |
| Centred insert sleeve | Built in | No | No |
500
planned founder spots
in this release
in this release
Free
to reserve and
lock your price
lock your price
100%
refundable any time
before it ships
before it ships
The one you can control
Age and genes are fixed.
Age and genes are fixed.
Heat is not.
A laptop on the lap, a hot seat, a long drive, a sauna round. That heat is the one input you can act on today, and it is the one NUMBNUTS is built to attack. Merino wool through the boxer body and centre sleeve, natural rubber at the waistband, and cooling exactly where it counts.
- Full refund any time before it ships
- Free delivery on qualifying orders
- Founder preorder price
$69.00
Founder price · target dispatch 30 September 2026
Choose size, then pre-order · $69.00
Take the 60-second Heat Check
Not ready to pre-order? Take the free Heat Check first. No card needed for the quiz.
The detailsIt goes in the middle.
It goes in the middle.
Not a side pocket.
The merino sleeve keeps the insert centred and separate from your skin.
Merino at the centre.
100% merino wool, matching the boxer body.
Targeted, reusable cooling.
Reusable inserts absorb body heat as they soften.
Natural rubber at the waist.
Natural rubber at the waist. Merino wool in the body and sleeve.
The movement
Welcome to the Cold Club.
This is the world we are building. Cold lockers, run-club drops and pop-ups in your city. Founders who join before public launch hold that status for life: first access to every drop, the founders’ Discord, and first invites when the pop-ups land in your city.
Claim founder status
Your first-drop system is your membership card. Our first founder allocation is planned for 500 spots.
Brand campaign imagery.
Who this is for
Most guys scroll past.
Most guys scroll past.
Founders fix it.
Same research. Same busy day. A choice about what you do next.
The guy who waits
Leaves the routine on autopilot
Keeps the laptop where it is. Never checks the fabric label. Tells himself he will look at his everyday heat habits another day.
The founder
Handles it tonight
Checks his heat habits. Chooses natural fibre. Makes a deliberate daily change instead of leaving his routine on autopilot.
You cannot change your genes. You can change what tonight looks like. Become a founder.
Straight talk
First drop. Clear terms.
One boxer. Two reusable inserts. No subscription or automatic repeat charge.
Simple by designOne payment today
We show you the research and its limits: Human Reproduction Update, Human Reproduction, and the original human and animal textile studies.
Research, in contextPeer-reviewed, not hype
Cancel before fulfilment for a full refund. After delivery, try your first one-boxer/two-insert bundle for 60 days, with no worn return required. One first-pair claim per customer. Read the guarantee.
60-day first-pair guaranteeClear before you commit
The founder offer
Two enemies. One system. Founder price.
$69.00 Founder price
Founder preorder. One payment today. No subscription.
For the man who takes his future seriously. Natural fibre against your skin. Targeted cooling at the centre.
- 100% merino wool boxer + centred merino-wool sleeve + natural-rubber waistband 1 included
- Reusable cooling inserts 2 included
- UK and US delivery on orders of US$65 or more (local-currency equivalent) Free
- Founder preorder price Locked
- Refund before fulfilment Guaranteed
Cooling Boxer + Inserts
Target dispatch 30 Sep 2026$69.00today
Founder preorder price
Choose size, then pre-order · $69.00Free delivery on qualifying orders · Full refund before fulfilment
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Why we built it
We got tired of being told to just relax and wait. Heat and plastic are two things you can fix today. So we built the system that attacks both, and made it something you actually want to wear.
Jaspal Rai, Founder, NUMBNUTS. One Third Group.
FOUNDER
PROMISE
PROMISE
Zero risk
Reserve now. Decide later.
Reserving is free and locks the founder price. Pre-order and you are refundable in full, no questions, any time before fulfilment. We are targeting dispatch by 30 September 2026, subject to final production confirmation. UK and US delivery. Free on orders of US$65 or more (local-currency equivalent). No subscription, ever.
Questions
Straight answers.
What exactly is NUMBNUTS?
A wearable cooling system for men: 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.
Why does natural fibre matter?
We choose 100% merino wool for the boxer body and centred sleeve. The small human polyester study tested a scrotal sling, not ordinary boxers; a separate dog study compared polyester with cotton, not wool. Neither proves that merino improves fertility.
Does cooling really help?
Scrotal cooling has shown a positive trend in small studies, but a systematic review found insufficient evidence for firm fertility conclusions. NUMBNUTS is designed for targeted cooling and comfort. It has not been shown to improve sperm counts or fertility.
Are sperm counts really declining?
Yes. A 2023 global meta-analysis estimated a 51.6% decline in mean sperm concentration among men unselected by fertility from 1973 to 2018, with a faster modelled decline after 2000. This is a population trend, not a measurement of your sperm or evidence about NUMBNUTS.
How is reserving free?
Join the founder list with your email and we hold your price before public launch. No charge, no card. Prefer to lock the first drop today? Pre-order, and it is refundable before it ships.
When does it ship, and what does shipping cost?
We are targeting dispatch by 30 September 2026, subject to final production confirmation, with tracking the day it leaves. We currently deliver to the UK and US. Orders of US$65 or more (local-currency equivalent) qualify for free delivery. Below that, the final charge is shown before you pay.
Where do you deliver?
We currently deliver to the UK and US. Delivery is free on orders of US$65 or more (local-currency equivalent). Below that threshold, the final charge is shown before you pay.
Is it discreet?
Yes. It wears like normal underwear and the insert sits in the center sleeve. Nobody has to know.
What is your refund policy?
Cancel for a full refund any time before fulfilment. After delivery, our 60-day first-pair guarantee covers your first one-boxer/two-insert bundle. Not for you? Email hello@numbnutsclub.com within 60 days for a refund, with no worn return required. One first-pair claim per customer. Full terms: numbnutsclub.com/pages/refunds-cancellations.
Free guides
Not ready to buy? Read first.
Everything we know about heat, fabric and sperm, with the studies linked. No email required.
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Summer Heat and Your Sperm: The Seasonal Dip Nobody Mentions
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Founder release. First drop.
