Soul Frame: Also called "sole frames" and "midsoles". Pertains to Aggressive skating. This is the hard plastic part that makes up the flat sole of the aggressive skate. Often measured in by whole sizes or combo sizes. They can wear out from grinding. They are the part the UFS frames mount to.
Midsoles: Same function as the soul frames
Grind inserts: These are sometimes used in conjunction with soul frames. They are attached to the bottom of the soul frame or midsole. The UFS frames attach to them. Often sold in 4 parts. 2 for the right skate and 2 for the left skate.
Tumor plates: Another form of "grind insert" used in the brand USD. Same function as the grind inserts.
Special Note: All aggressive skates have these parts. The names differ depending on the brand name. Razor skates, USD, Deshi, Rollerblade, K2, Salomon and Roces all have these parts.
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