"Designed to fit into tight areas to remove painted-over, rounded-off, rusted-tight and stubborn nuts and bolts. Allows use of 3/8 in.-drive ratchet, flat wrench, locking pliers or impact wrench. Made of high-carbon steel. Left-handed spiral teeth. U.S.A. Metric Socket Size mm 8-19, Pieces qty. 5, Measurement Type Standard SAE/Metric, Material Type Carbon steel, Drive in. 3/8, SAE Socket Size in. 5/16-3/4, Storage Type Rail. Includes sizes 5/16 in. 8mm, 10mm, 13mm, 11/16 in., & 3/4 in. 19mm"