The Starrett 91C tap wrench body holds 1/4" to 5/8" taps with 5/32" to 3/8" 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.)1/4" to 5/8"Capacity size (metric)6.35 to 16 mmBody length (U.S.)12"Body length (metric)300 mmSquare shank (U.S.)5/32" to 3/8"Square shank (metric)4 to 9.5 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.