7mm's are a smaller radial/conical shape with dimensions 7.0mm x 5.5mm also feature a rounding to the wheels edges to give real feel. These sit right about to the locknuts.
8mm's are a different take on a bowl wheel, with rounded edges to give that radial/conical look, these are 8.0mm x 5.5mm wheel, smaller diameter than most bowl wheels. These sit right about to the locknuts.
