Hutch 25T Sprocket is designed for 20" freestyle applications such as the 2015-present modern-technology Trick Star which are designed for the 25-9 gear ratio. This sprocket includes the traditional boss-drive method similar to old-school 1980's cranks, and is compatible with the current boxed Aerospeed crank set. The Hutch sprocket's two colors have the appearance of a two-piece disc/chainring, and the holes are designed to allow you to put chainring bolts of your color choice in the 5 outer holes to enhance that appearance of the old-school two-piece design. The result is a modern version of the Hutch Aerospeed Disc and chain ring yet in a smaller 25T one-piece design.