YOU CHECK YOUR FOOD. CHECK YOUR FABRIC.
You read the food label.
When did you last read this one?
Polyester is plastic fibre. We went merino.
100% merino body & sleeve. Natural-rubber waistband. Two reusable cooling inserts.Thinking about fertility? Start by knowing your everyday heat habits.
YOUR UNDERWEAR. YOUR CALL.
Same standards. Two ways to start. Merino for your daily rotation, or merino with targeted cooling.
1 merino boxer + 2 reusable cooling inserts.
3 same-size merino boxers. No cooling inserts.
Full order prices shown. One-time preorders, not subscriptions. Nothing charged today. See payment and dispatch terms below.
One boxer. Two inserts. Every part has a job.
15% off your first Cooling Boxer + 2 Inserts with FOUNDER15 until 1 November 2026, 00:00 UTC. Three-pack excluded. Final eligibility checked at checkout.
Select a size to continue.
One-time preorder. No subscription. Nothing charged today. Card saved securely at checkout and charged once on 30 November 2026.
Keep Your Pants Guarantee. Try your first bundle for 60 days from delivery. Not for you? Request a refund; no worn return. One claim per customer.
02 / YOUR NEXT PAIR SHOULD DO MORE
Merino body. Natural-rubber waistband.
Targeted cooling. Two reusable inserts.
NOT JUST A DIFFERENT LOGO. A DIFFERENT BUILD.100% merino wool through the body and centre sleeve, designed for next-to-skin wear. Individual comfort varies. Natural rubber is at the waistband, not in the sleeve.
A natural-rubber waistband. The centre cooling sleeve is merino, not rubber.
Two reusable cooling inserts. Place one in the merino sleeve and follow the supplied use and reset instructions. No extra accessories.
Product visualisation of the cooling boxer and two inserts.
01 / THINKING ABOUT SPERM QUALITY?
Some future plans deserve attention before they feel urgent. If sperm health is on your mind, start with the everyday heat habits you can review. The laptop. The hot bath. Hours in the same chair.
In 29 volunteers, scrotal temperature rose up to 2.8°C during an hour with a working laptop on the lap.
The same sitting position without a laptop raised temperature 2.1°C. The study measured temperature, not sperm or pregnancies.
Sheynkin et al. · Human Reproduction ↗Overnight air cooling plus behavioural changes was associated with improved sperm counts in men with abnormal semen parameters.
This was a different cooling intervention in a selected clinical group, not a NumbNuts trial. It does not establish that these boxers improve fertility. Our inserts are not for sleeping in.
Jung et al. · Reproduction ↗All 23 human testis samples in this study contained microplastics. A reason to ask better questions about everyday materials.
Detection does not prove harm or the source of exposure. Human sperm counts were not measured. This does not show that plastic from underwear enters through skin, or that merino improves sperm.
Hu et al. · Toxicological Sciences ↗NumbNuts is a comfort product, not a fertility treatment. Worried about fertility? A clinician and semen analysis can tell you what a quiz cannot.
Explore the full research ↗YOUR ROUTINE IS NOT EVERYONE ELSE’S
You know the routine. Find the bits you may have stopped noticing.
8 quick questions + 5 optional research questions. Email, marketing and research are optional.
03 / BEFORE YOU DROP YOUR PANTS
A SERIOUS IDEA. A RIDICULOUS NAME.
Your standards should not stop at your waistband. We made NUMBNUTS for the part of your routine that usually gets the least thought: the first thing you put on.
One NumbNuts boxer with a 100% merino body and centre sleeve, a natural-rubber waistband, and two reusable cooling inserts. No case or extra accessories.
The three-pack gives you three same-size merino boxers, without cooling inserts. The cooling bundle gives you one merino boxer and two reusable inserts. Both use natural-rubber waistbands. The 60-day first-bundle guarantee applies only to your first cooling bundle.
See the three-pack →Place a reusable cooling insert in the merino sleeve. Follow the supplied use, reset and care instructions between sessions. Do not put it directly on skin or sleep in it.
No charge today with the charge-later preorder option. Save payment details securely at checkout; your card is charged once on 30 November 2026. Checkout confirms the payment terms, delivery charges and taxes. Cancel free before fulfilment. November 2026 is the target dispatch, not a guaranteed date.
Yes. The current Keep Your Pants Guarantee covers your first bundle for 60 calendar days from delivery, with no worn return needed. One claim per customer; second bundles and repeat purchases are excluded. See the full live refund terms.
We cannot promise that. NumbNuts has not been tested for fertility outcomes. We explain the published heat research, but the product is for comfort. Fertility concerns deserve advice from a qualified clinician.
The boxer body and centre sleeve are 100% merino wool, with a natural-rubber waistband. Follow the garment care label supplied with your production pair. Final washing and drying instructions will accompany the garment.
Remove the cooling inserts before cleaning the boxer. Garment care and insert care are separate. Follow the supplied insert-use instructions. Never put an insert directly on skin or use it while sleeping.
YOUR NEXT PAIR IS A DECISION. MAKE IT COUNT.