Includes: (1) STD500NP, (1) STD1000DGNP, (1) STD2000DGNP & (1) SDGMINI | Special nickel alloyed steel heat treated for durability. Non-plated material with light oil coating to prevent rust. | Centers the holes on pipes, dowels & outside corners. Flat side allow 90° drilling into flat surfaces-just clamp and drill.. Automatically squares up the drill with the surface. Alignment marks on both sides