DeFender(TM) M2 has an ultra-secure quick release mounting system that easily adjusts from 25.4 to 34.9mm, easily fitting standard and oversized seat posts.The two-pivot arm articulates for improved tire coverage and perfect bike fit.A stiff engineering grade plastic support frame is comolded to a softer more flexible material at the trailing edge for greater durability.A highly polished underside helps prevent dirt buildup and aids in cleaning.Size (L x W x H) 40 x 10 x 12 cm 15.8" x 3.9" x 4.7"