SURPRISINGLY USEFUL We can officially only rate these warmers at UPF 50+, but in our laboratory tests they actually blocked 99.8 percent of damaging UV rays. We used a polyester base that is not only more effective than nylon at blocking UV rays but is also much better at keeping you dry, which means these arm sleeves are better in both cooler and warmer conditions. We’ve kept the construction very clean to eliminate seams that can rub, and we used our double-sided silicone elastic to make sure they stay in place. They fold up extremely small, so they’re great to stick in your pockets for your next big mountain day.
Solare fabric keeps the chill off without causing overheating
UPF 50+ protection
Polyester based for excellent moisture management
Double-side silicone elastic at top for excellent grip
GETTING IT RIGHT The Thermoflex warmers concentrate on getting everything just right. The fabric is extra warm and stretchy, the fit eliminates any extra fabric, the silicone gripper at the top prevents the warmers from falling down, and the cross-wrap cuff at the bottom gives a touch of extra comfort.
NANO FLEX ALL-CONDITION WARMERS Choose Nano Flex for warmers that are great in dry conditions but also give some extra protection and warmth in wet conditions. We invented the category of water-protective thermal fabrics, and Castelli's proprietary Nano Flex is often imitated but never equaled. No compromises for any conditions.
Water-repellent thermal and breathable Nano Flex fabric
Flat-lock stitching with single seam
Double-sided silicone grippers to keep warmers in place