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Castelli Nanoflex Arm Warmers

The Nanoflex Arm Warmers are designed to be used in slightly colder temps and for inclement weather. To understand how well these work in the right conditions, you need have an understanding of the Nanoflex textile. Nanoflex starts out as the Castelli Thermoflex fabric. This fabric is then treated with a 5 layer microfilament coating that provides a weather barrier. Thermoflex + proprietary microfilament coating treatment = Nanoflex.

This Nanoflex treatment consist of a coating that is constructed from millions of microscopic filaments. The grouping of these filaments provide protection from wind and water, but are just porous enough to release moisture and perspiration from within. Nanoflex is soft and elastic which leaves the garment feeling comfortable yet supportive. Etymology of Nanoflex comes from combining the metric prefix nano with the word flex. In this case Nano means many and flex refers to a soft flexible fabric. Now combine nano with flex and you get Nanoflex, the magical material that provides millions of microfilaments that coat the thermal based fabric Thermoflex. This Nanoflex/Thermoflex combo provides ample protection from the elements in a flexible and comfortable garment. The amount of breathability vs wind and weather protection is unrivaled.

Overall, the Nanoflex arm warmers have a very protective feel. They work in a wide 45-65ºF temperature range. A detail we like very much is silicone grippers on both the inside and outside to keep the both the arm warmers and the jersey sleeve in place. Nanoflex works best when it is a snug fit, so do not expect these to feel loose with bunching and a gathering of material. They are designed to fit tightly.


  • Water-resistant Nanoflex fabric
  • Good breathability and flexibility
  • Great in every possible condition
  • The ultimate protection for your arms
  • Dual top silicone grippers
Sale Price
Reg Price $59.99


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