This Irwin Bolt Fastener Remover Expansion 5-piece set is used 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 3/8 inch square drive and has hexagon flats for use with a spanner or adjustable wrench. Universal lobular design for all types of fasteners. Sizes: 5/16in (8mm), 10mm, 13mm, 11/16in, 3/4in (19 mm).