Nathan Light Streak Vest Safety Anatomical shape offers full range of motion without interrupting arm swing Adjustable shoulder straps for optimal fit customization 3 front white super bright LED's and 3 back red super bright LED's with multi settings for high visibility and added safety Powered with replaceable watch battery Available in S/M or L/XL unisex; S/M 24-40in. L/XL 38-45 in