DeFender 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 co-molded to a softer more flexible material at the trailing edge for greater durability. Our highly polished underside helps prevent dirt buildup and aids in cleaning. Fits MTB 26" tires.