A set containts 4 wheels Diameter: 57mm Hardness: 90A

Ground Control is an American brand best known for their Frames, Their riders are pro skaters like Martin Danning, Josh Glowicki, Nils Jansons.
Make sure that the diameter is correct for your type skate, the width of inline skate wheels are always the same, If you are not sure these wheels will fit your skate, you can always contact us

More information about wheels in general here:
http://thisissoul.com/general-info-on-inline-skating-wheels

More information about ground control wheels can be found here:
https://www.gc-uprising.com/wheels