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Fertility-Saving Briefs
The cotton brief that holds the boys at 95°F while the sauna cooks at 200°F. Stop choosing between your longevity routine and your fertility.
95°F Target Zone
Swimmer Protection
30 Min Active Cold
Cold-Plunge Ready
US Free Shipping
3-5 Day US Delivery
30-Day Money-Back Guarantee
What is it?
Cotton briefs with an insulated sewn-in pouch that holds 2 freezable BPA-free gel inserts. Freeze the inserts 45 minutes before your sauna, slide them into the pouch, wear the brief under your sauna towel. The gel holds your scrotum at the natural 95°F target while your core body hits 106°F. The rest of you gets the full longevity benefit of the heat. Your swimmers do not get cooked.
Why would I need it?
One 20-minute sauna at 185°F raises scrotal temperature enough to drop motile sperm count by more than 50%, and the damage does not clear for 5 weeks. If you sauna 2x a week, the damage counter resets before you recover. This is the fix Bryan Johnson figured out after 238 sessions, that Huberman confirms in his newsletter, and that Dr. Eisenberg at Stanford recommends on air. It is also the single biggest lifestyle variable in male fertility, above diet, above sleep, above alcohol.
How quickly will I notice results?
First session. Your scrotum drops into the 95°F zone the moment you sit down. You feel the cold through the cotton barrier in about 10 seconds. Most guys report the sauna suddenly goes quiet because the background thought ("am I ruining this?") shuts off. On the biology side, sperm parameters rebound on the 74-day cycle. The Jung 2005 cooling study saw sperm count rise from 23.9 million to 39.6 million in 12 weeks. Turek's UCSF data showed a 491% average increase in total motile count for men who stopped overheating.
Do you offer a guarantee?
Yes. 30 days, no questions asked. Wear them in the sauna for a month. If they do not keep the boys cool, if your session does not run longer, if the heat anxiety does not shut off, email us for a full refund. You cover return shipping. We are that confident.
Real People. Real Results.
Raw, unedited reviews
4 Signs Your Sauna Is Cooking Your Swimmers
If your 4-a-week sauna habit is running above 99°F, the signs are already there. You have just been filing them under "uncomfortable"
Why It Hits Harder
After 35
The boys run 4 to 5°F cooler than your core for a reason. After 35, one 200°F sauna session stacks damage that takes 74 days to surface in your ejaculate:
Cook Production
Cook Production
Sperm production collapses the moment the scrotum crosses 99°F.
Fragment DNA
Fragment DNA
Heat shreds the DNA inside the sperm head. Fragmented DNA drives failed implantation and early miscarriage, even when count and motility look fine on paper.
Stall Rebuild
Stall Rebuild
One hot session resets the 74-day rebuild clock. Sauna twice a week and the counter resets before your body finishes recovering.
Compound Loss
Compound Loss
Session over session, the damage stacks faster than recovery, and each passing year of age shortens the window for any of it to come back.
How Navulis Works For You
The 2-part cooling system that holds the boys at 95°F under 200°F heat.
Only Pure, Non-Toxic Materials
100% Cotton Body
Third-Party Verified
Lab-Tested At 212°F
BPA-Free Gel
Zero Microplastics
No Phthalates
Why Sauna Guys Pick Navulis Over DIY
Your Swimmers Will Not Rebuild Themselves
Do not let 200°F sessions, fragmented DNA, and the 74-day regeneration cycle drain your count in silence. With one cool brief and 30 seconds of prep per round, you can:
Lock 95°F
Block Damage
Rebuild Count
Save Ritual
Frequently asked questions
Is there actually evidence that cooling the groin in a sauna protects sperm?
Yes. The Garolla 2013 study in Human Reproduction saw 15 minutes of sauna twice a week drop motile sperm count more than 50%, with recovery taking 6 months. The Jung 2005 cooling trial saw sperm count rise from 23.9 million to 39.6 million in 12 weeks of scrotal cooling. Brown-Woodman 1984 saw at least a doubling of sperm density and motility in 65% of men after targeted cooling. Huberman explicitly prescribes a cool pack in his deliberate-heat newsletter. Bryan Johnson ran his own protocol across 238 sessions and his fertility markers now put him above 99.6% of men under 25.
How long does one gel insert stay cold?
30 minutes of active cold after a 45-minute freeze, which matches one full sauna round at 185°F to 200°F. After the gel thaws, the insulated pouch keeps working as thermal insulation and holds the boys under the 99°F damage threshold for the rest of the session. Most guys own 2 pairs and rotate sets across back-to-back sessions so they are never without a cold insert.
Do they fit like regular underwear?
Yes. 100% cotton body, cotton-elastane waistband, anatomical fit. The gel-pack pouch sits flush against the scrotum and does not visibly bulge under a sauna towel or standard gym shorts. Sizes run S through XXL with waist ranges on the size chart. The cotton has minimal stretch, so if you are between sizes, go up.
Can I wear them in a cold plunge or hot tub?
Yes to both. In a cold plunge the brief actually re-freezes the thawed gel inserts, which is a bonus if you run contrast therapy (sauna-plunge-sauna). In a hot tub the same 95°F protection applies, and since hot tubs sit around 104°F and sperm production collapses above 99°F, the brief earns its keep faster in the tub than in the sauna.
Does the cold hurt, cause frostbite, or why not just use a bag of frozen peas?
No frostbite. The cotton body is the thermal barrier between the frozen gel and your skin, which is exactly why a loose ice pack in your shorts is risky (direct contact, frostbite possible, flagged by Huberman on air) and the engineered brief is not. A bag of frozen peas slides off the anatomy that needs cooling, dies inside 5 minutes in a 185°F sauna, and makes a mess as it thaws. SaunaArmor holds 2 anatomically shaped BPA-free gel inserts flush against the scrotum through cotton for a full round. You feel cold. Your skin does not burn.
I am not trying to conceive right now. Do I still need this?
Sperm you produce today reflects heat exposure from 10 to 12 weeks ago. Global sperm concentration has dropped 51% since 1973 and the decline is accelerating. The biohackers who discovered at 34 that their count was running in the low-fertility range could not reverse-time their sauna habit. If you plan to have kids inside the next 5 years, a $49 brief you already wear in the sauna is the cheapest insurance you will ever buy.
How do I wash them?
Remove both gel inserts first, they do not go in the washing machine. Cold wash the brief, hang dry or tumble dry low. The 100% cotton body holds its shape across hundreds of cycles. The gel inserts wipe down with soap and water and go back in the freezer. The inserts are reusable forever with no loss in cold duration.
What if they do not work for me?
30-day money-back guarantee, no questions asked. Wear them in the sauna for a month. If the boys do not stay cool, if your session does not run longer, if the heat anxiety does not shut off, email us and we refund in full. You cover return shipping. We are that confident.