This set consists of 4 detailed resin wheels for the Irving Napier land speed car that set a record of 231 mph in 1929. The Profil24 kit, which these are designed for, has wheel castings that are very rough, and you could spend hours on each one and not get them to look anywhere as good as these! A esoteric product for sure, but if you have this kit, you NEED these wheels! I'm told they could be used on other land speed cars of the time. Wheels are 40mm in diameter.