Features: Compatibility: Convert a multi speed hub to single speed wheel. for all for or Sram 7 to 11 speed cassette type hub body, mountain and road. NOTE: It will NOT covert the hub into fixie, so the hub is still a freewheel hub. High quality stainless steel: The flywheel is made of high-resistant stainless steel, the strength and hardness are twice that of ordinary 316 stainless steel, and the hardness reaches 18 degrees. Chain Size: The sprocket is for the chain width from 1/2" x 3/32" to 1/2" x 11/128". ( 7 speed to 11 speed chains). You can use your original chain! With a choice of different sprocket teeth selections, you can for always get the perfect pedaling ratio. Specifications: Material: Stainless steel Color: silver Teeth: 12T/13T/14T/15T/16T(optional) Processing technology: CNC cutting Packing size: approx. 12x8x2cm/4.72x3.15x0.79in Applicable: Mountain bike multi-speed to single-speed, suitable for 7/8/9/10/11-speed chain Package Includes: 1 x Single-Speed Bike Freewheel note: No retail package. Please allow 0-1cm error due to manual measurement. pls make sure you do not mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you!