CR-2 The CR2, as with all of our chainrings, starts off as a bland 6mm thick plate aluminum but by the time we get done with it, it's become so much more. The CR2 incorporates a huge FireEye hexilogo machining right smack in the middle of the ring. It saves weight while also incorporating design and function. Super tough, built to take a punishment, and look good doing it. It's available in both 36T and 38T configurations and compatible with both 19mm and 22mm axles through the use of the provided spacers. Material: aluminum 6061-T6 Spildle Diameter: 23.8mm (with 22mm and 19mm spacers) Thickness: 6mm Sizes: 36t and 38t / 2.3mm (1/8") Color: black Surface finish: sand-blasted and anodized Logo: CNC logo