GearWrench Piston Ring Groove Cleaner The GearWrench Piston Ring Groove Cleaner effectively removes carbon from ring grooves 2 to 5” (51mm to 127mm), two 5 bladed cutters cover all major piston ring grooves in SAE and Metric sizes, the cutters rotate to any selected size, locking in place with hold-down nut, and Included Cutter #1: 1/16”, 5/64”, 3/32”, 1/8”, 3/16”, and Included Cutter #2: 1.5mm, 2.5mm, 3mm, 4mm, 5mm.