Reverse spiral flutes engineered to provide maximum gripping power to easily remove broken, damaged, or rusted nuts, bolts and screwsHigh carbon steel ensures longer life and greater durabilityUniversal lobular design fits all types of fastenersPowerful rare earth magnets, with four times the hold of standard magnets, for secure attachment to work and storage surfacesNon-mar foam backing to protect against scratchesClips feature ball-lock retention design for easy on / off storageSpecificationsItem #DescriptionContents187622814-Piece Impact Bolt-Grip Rail Set1/4" / 6mm, 5/16" / 8mm, 3/8", 10mm, 7/16" / 11mm, 12mm, 1/2", 13mm, 9/16" / 14mm, 5/8" / 16mm, 17mm, 11/16", 3/4" / 19mm 3/8" Drive, 1/4" to 3/8" Adapter