5-arm, for 10-/11-speed, 130mm circle diameter, aluminium 7075 T6, with ceramic-teflon coating. The ceramis coating provides for better rigidity, durability and abrasion resistance. The teflon cover reduces the friction of the chain by 80%, provides for much quieter running, permament lubrication improves the sfifting function. These chain wheels are durable / light / precise / maintenance-free.Specifications:- Amount of teeth: 40- Attachment: 5-hole- Circle diameter: 130 mm- Weight: 0.97 kg