Often the kit manufacturers produce wheels for the kits which aren’t as accurate as some modelers demand. The term AMS comes to mind here. Anyway, Res-Im has produced improved resin wheels for the late model 1/144 MiG-21.
Only the main wheels are done for this set, as all of the 1/144 MiGs I found had the gear leg molded onto the nose wheel. This shows up in the photo below which shows the Airfix wheels and the Res-Im wheels, with the nose wheel firmly molded onto the gear leg.
There’s no real assembly to this set, you just paint the wheels. Additionally, there are no instructions, but they aren’t needed. I painted the wheels first before I removed them from the pour sprue. Then I cut the wheels off the sprue, cleaned up the attachment points, and finished painting the tires.