This Irwin® Bolt Grip Fastener Remover 5 Piece Base Set is ideal for removing rounded, rusty or painted bolts. It has a unique reverse spiral flute design which securely grips and removes stubborn nuts and bolts. They can be used with a hand ratchet 3/8inch square drive and has hexagon flats for use with a spanner or adjustable wrench. They are made of high carbon steel for long life and durability. Supplied in a carrying case. Specification: Sizes: : 3/8in (9mm), 7/16in (11mm), 1/2in (13mm), 9/16in (14mm), 5/8in (16mm).