Fowler Machinist Screw Jack Set Set consists of 2 machinist jacks supplied in a shop hardened case. Individual jacks consist of a heavy, steel cast base with adjustable steel screw and tilting swivel head, with a lock nut for permanent positioning. Features include... 1-1/2" jack base for added stability. Range: Min. 3" / Max. 4" Lifting capacity: 1000 lbs.