Paul Chain Keeper. Features: Machined aluminum Chain Keeper works either as a Singlespeed guide or with a 1X multi speed set up Clamp version mounts to the seat tube in place of the front derailleur and comes in 3 sizes Wide mouthed chain block and adjustable rod allow for precise alignment Use chain keeper extension (PC-2909) to fit some difficult frames (full suspension, tapered seat tube) Not intended for DH, FR, or big hit use Made in USA Specs: Color:black Clamp Size:28.6mm