The right abrasive for lapping the final fit between semi-auto slides and frames, rifle bolts and receiver raceways and any other application where a super-close fit or silky smooth mechanism is required. #600 and #800 grit aluminum oxide abrasive crystals in a long lasting petroleum base that's water soluble for fast, easy cleanup in soap and water. Aluminum oxide crystals are smooth and rounded in shape, so they won't embed and continue to wear the part after cleanup. SPECS: Aluminum oxide. 4 fl. oz. (118ml).