The Madera Helm Spline Drive sprocket is manufactured from 7075 Aluminum in the USA. This sprocket requires no sprocket bolt. Instead, it has a hardened Cr Mo steel insert in that matches up to the 48 splines on the BB axle for pure, direct power transfer. Work on 19mm spindles only. section Product Specs TYPE: Spline Drive
Material: Alloy WEIGHT: 81g / 2.85oz