UNF (black): 1/4"-28, 5/16"-24, 3/8"-24, 7/16"-20, 1/2"-20, 9/16"-18, 5/8"-18. UNC(silver): 1/4"-20, 5/16"-18, 3/8"-16, 7/16"-14, 1/2"-13, 9/16"-12, 5/8"-11；. The thread repair kit is made of the highest quality carbon steel and tempered at high temperatures for great strength and maximum durability.