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