Now available exclusively throughStone Boss, the new Panther 4-inch FlexCup is a super smooth, extremely quiet cup wheel, mounted on a rubber flexible backer. It is designed for low RPM tools, and it works exceptionally well on air polishers.The diamond bonding technology uses a vacuum furnace method of sintering, which produces an aggressive tool and leaves a finish quality that appears finer than the grit size used. The vacuum sintering technique allows for maximum crystal strength, which results in a tool that stays sharper longer, cuts cleaner and has outstanding finish quality, reports Stone Boss. Maximum RPM is 3500, and it is for wet use only.