The Castelli Thermoflex Knee Warmers is a best seller due to the basic and solid design that works without issue with every outing. They feature a good fit. And while this doesn't sound very exciting, it will make or break a garment that fits around a knee of a cyclist. Castelli's anatomical and tapered fit of the Thermoflex knee warmers guarantees you will not experience bunching or gathering of excess material in the back of the knee, nor experience the dreaded pulling effect on the front of the warmer. The superb fit makes them feel like they are a natural extension of the skin.
The interior of the arm warmers have plush and inviting brushed fleece whose duplicate task provides thermal value and moisture management through perspiration wicking. The fleece has tiny filaments, each with hollow cores to trap heat and keep it against your skin, while the porous nature of the Thermoflex fabric allows for simultaneous breathability. Thin silicone grippers on the inside of each end of the warmer do a good job at keeping these in place while cycling.