The CURT hitch-mounted tray-style bike rack promotes your biking experience unlike any other because of its unique, three-point support system. It is made to be easier to use and keep bikes more secure, holding them at three points of contact. Instead of hanging the bike by its crossbar, the loop-like tray-style arms cradle the bike's wheels, holding it securely on each end. The third point is an adjustable padded arm that slides up and down and tightens over the crossbar, keeping the entire bike firmly held in place. Both the tray arms and the vertical padded arm are highly adjustable and can fit virtually any size bike, from a giant adult mountain bike to a single-gear kids' bike. For fat tire bikes, these add-on tray-style arms are designed to replace the existing arms on the tray-style bike rack, allowing for tires up to 4 7/8" wide. The fat tire arms are fully adjustable to fit most bike sizes, and they are covered in a durable black powder coat finish. Two fat tire arms are included in this package, and they are compatible with the CURT #18084 or #18086.