Westward Inside Spring Caliper 40L730 Spring and firm joint calipers are measuring tools consisting of two symmetrical legs that meet at a hinge, forming a jaw. The jaws are adjustable and the contact points located on the outer sides of the legs can be used to measure the distance between them. These calipers are commonly used in metalworking, machining, and woodworking to take indirect inside measurements. Range / 0.6 inch to 6.5 inch, 15 mm to 165 mm Joint Type / Spring Maximum Measurement / 165 mm; 6.5 inch Maximum Measurement - Inch / 6.5 inch Maximum Measurement - mm / 165 mm Minimum Measurement - Inch / 0.6 inch Minimum Measurement - mm / 15 mm Nut Type / Solid Caliper Material / Steel Leg Style / Flat