Extractor allows for easy removal of broken studs, bolts socket screws and fittings. The spiral design allows for increased grip. Set comes packaged in an organized storage case. Notes:#1 for 3/32" - 5/32", 2.5mm - 4mm, #3 to #6#2 for 5/32" - 7/32", 4mm - 6mm, #6 to #12#3 for 7/32" - 9/32", 6mm - 8mm, #12#4 for 9/32" - 3/8", 1/8" NPT, 1/8" BSP, 8mm - 10mm#5 for 3/8" - 5/8", 1/4" NPT, 1/4" BSP, 10mm - 16mmFeaturesSet contains extractors #1 through #5Left-hand spiral design, for removal of broken studs, bolts, screws and fittingsHigh carbon steel, square driveExtractor size and recommended drill bit size are etched on each extractor