The ultrex interchangable rings are the first of it39s kind in scootering to give riders the option to interchange their urethane when need be the wedge shaped ring is designed for the 2 hub halves to tighten together concentricity to allow quick disassemble with a 4mm allen key110mm diameterripper 89a duroanodized ring for easy installation and replacementweight 130gsold as single wheel ring