Use ultralight high-strength AL7075 Aluminium Alloy with high quality CNC machined, light weight but high strength. Material: 7075 aluminum alloy CNC; nylon Spec: BB mount BSA68 / ISCG-05 Range: round : 32T-38T Weight: CG-03 143g, CG-04 200g Package: 1 pcs chain guide and screws BB mount adapter is included Fit for BSA 68 bottom bracket Adapter Thickness: about 3mm Center hole diameter : about 35mm Perfect for 1x system