This mountain bike cassette is made of metal and is suitable for mountain bike use. It has an 11-40 ratio and is the CSMS8 model. This cassette has 11 gears and uses Fluid Drive Plus technology. The gear ratio is 11-40T and the tooth combination is 11-13-15-17-19-21-24-28-32-36-40. The cassette is made of high-quality material, with an aluminum spider, spacer, and cog that are anodized black. The sprockets are made of Hi-Tensile Steel. The cassette has a silver metallic finish and features milled holes for weight reduction. The cassette weighs 429 grams. Product specifications - Model: CSMS8 - Gears: 11 (wide ratio) - Function: Fluid Drive Plus - Toothing: 11-40T - Tooth combination: 11-13-15-17-19-21-24-28-32-36-40 - Material: - Spider, spacer and closing ring: Aluminum / black anodized - Sprockets: Hi-Tensile Steel - Finish: Silver metallic - Milling holes for weight reduction: Yes - Weight: 429 grams