7 Pieces – 45 Degree Brass Muzzle Lapping Tools. You Can Use These With The 600 Grit Silicon Carbide Lapping Compound To Remove The Micro Burrs On The End Of The Lands And Grooves At The Barrel Crown. It Has A Range From .17 To .50. The Shank Is 3/8″ Diameter. It Can Be Used With A Hand Drill At Low RPM. It Can Be Used After A New Crown Is Cut Or To Smooth Out An Old Crown. Made In USA. Thanks For Looking At Our Auctions.