These are 2-1/4" Super Lite Wheels from Dubro. FEATURES: Black impact-absorbing foam construction pre-mounted. Gray plastic 7 spoke rims. Five rib tread design. INCLUDES: Two 2-1/4" Super Lite Pre-mounted Wheels REQUIRES: Wheel collars to hold them on the axle. May require reaming out the hole to mount on larger axle. SPECS: Diameter: 57.1mm (2-1/4") Axle Diameter: 4.4mm (.176") Width: 19.7mm (.776") Weight: 8.14 grams per wheel