5 pieces BOLT-GRIP Expansion set is used for when you are faced with a rounded-off, rusted-tight or painted-over bolt, bolt extractors will break it free. The reverse spiral flutes are designed to bite down to provide maximum gripping power. High carbon steel ensures longer life and greater durability. The universal lobular design fits all types of fasteners. Set includes plastic case and bolt extractors to remove bolts sizes: 8mm, 10mm, 13mm, 19mm, 5/16", 11/16", 3/4" in drive size 3/8".