The Castelli Thermoflex 2 Arm Warmers are made from a soft and stretchy Thermoflex fabric. This traditional arm warmer offers the softest, most luxurious fabric combined with careful attention to construction details. The dual-sided silicone gripper elastic at the top prevents them from sliding down. The Castelli Thermoflex 2 Arm Warmers are luxuriously warm and stretchy in dry conditions but are not intended for wet conditions.