Tonsiki 5Pcs 50 Size Large Cobalt HSS Step Titanium Cone Drill Hole Cutter Bit Set Tool for Plastic, Aluminum, Copper and Stainless Steel Size:3/16" to 1/2"(3/16'', 1/4'', 5/16", 3/8'', 7/16'', 1/2''),1/8" to 1/2"(1/8", 5/32", 3/16'', 7/32", 1/4'', 9/32", 5/16", 11/32", 3/8'', 13/32", 7/16'', 15/32" , 1/2''),1/4" to 3/4''(1/4'', 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4"),1/4" to 1-3/8''(1/4'', 3/8", 1/2", 5/8", 3/4", 7/8", 1", 1-1/8", 1-1/4", 1-3/8"),3/16" to 7/8"(1/4'', 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4", 13/16", 7/8") Classic high speed steel with titanium coating for proven capability and durability in drilling holes in plastic, aluminum, copper, stainless steel and many other types of sheet metal Cobalt coated to reduce friction and run cooler,increases cutting speed with self-centering and prevents walking, clears chips faster and allows particles to escape easily. Large bit has 3-sided shank and small bits have hex shank to prevent slip in drill chuck Set includes a sturdy aluminum organizing case for secure storage and easy carrying