Four double edged cutting/gripping sides with 8-points of contact to make non-slip engagement with the bolt/screw. Ensures removal of even the toughest bolts/screws. Supplied in storage case. Four double edged cutting/gripping sides. 8-Points of contact to make non-slip engagement with the bolt/screw. Ensures removal of even the toughest bolts/screws. Contents: #1; 3.2-4.2mm(3/16"-1/4"), #2; 4.8-7.1mm(5/16"-3/8"), #3; 6.4-9.5mm(7/16"-1/2"), #4; 8.7-12.7mm(1/2"-9/16"), #5; 11.1-15.9mm(5/8"-3/4"). Supplied in storage case.