4 Piece 1/4-1/2″ Double-End Boring Bar Set ~ Includes the following: one 1/4 X 5″ that takes a 5/32″ round tool bit, one 5/16 X 5″ that takes a 3/16″ round tool bit, one 3/8 X 6″ that takes a 3/16″ round tool bit and one 1/2 X 6″ that takes a 3/16″ square tool bit. ~ Machined from selected steel for greater strength and rigidity. ~ Broached holes accept high speed steel and carbide tool bits. ~ Black oxide finish. ~ Bars have one 45° end and one 90° end.