Sport Direct AWE 6061 Alloy Quick Release Seat Clamp 31.8mm black The Seat Clamp & Lever Are Made From 6061 T6 Extra Lightweight & Strong Alloy Material Quick Release Lever For Easily Adjusting the Saddle Height Fits Onto 31.8mm Seat Post, Tensile Strength 310MPa Low Weight: 40g, Hardeness Vickers 100HV, Shear Strength 190MPa 6061 - T6 Alloy Is A Medium to High Strength Heat Treated & Artificially Aged Alloy. It Has Very Good Corrosion Resistance And Very Good Weldability. Extensively Used In The Aerospace & Military Industries