This set of four hub caps is the perfect replacement part for your Radio Flyer wagon or trike or scooter. Designed to fit a 3/8 inch axle. They are easy to install and will fit snugly on the wheels of your Radio Flyer trikes and wagons that use 3/8” axles. Hub caps are hammered on. These hubs were sent directly to us, Cloud Nine Toys in Sudbury Massachusetts, by Radio Flyer.