The Starrett 91B tap wrench body holds 3/16" to 1/2" taps with 5/32" to 9/32" square shank diameters and is used to tap workpieces (requires taps, not included). A plunger-type spring-operated knurled sleeve applies and removes the tap when pressure is applied. Tempered gripping surfaces firmly hold square or round shanks. The tap wrench has a 9" overall body length.SpecificationsCapacity size (U.S.)3/16" to 1/2"Capacity size (metric)4.7 to 12.7 mmBody length (U.S.)9"Body length (metric)225 mmSquare shank (U.S.)5/32" to 9/32"Square shank (metric)4 to 7 mm The L.S. Starrett Company manufactures precision measuring tools, metrology and testing equipment, and saw blade products. The company, founded in 1880, is headquartered in Athol, MA.