Equipped with low friction ceramic bearings for ultra-smooth glide and exceptional durability. Narrow Wide tooth profiling ensures ultimate chain retention.. Composite material provided by EMS swiss, with 40% glass-fibre mixture.. Lubricated with special ceramic light oil for extra smoothness.. Compatible with Sram 12 speed.. Specifications Compatibility: Sram. Part materials: Grivory EMS. Bearing material: Ceramic. Gears Compatibility: 12 speed. Pulley size: 12 + 14T. Narrow wide: Yes.