Westward 40L724 Outside Firm-Joint Caliper External spring and firm joint calipers are utilized for taking indirect measurements. They are adjusted until their legs make contact with an external diameter, groove, or other feature and then locked in place. The distance between the legs is measured using a ruler or high-precision gauge. These calipers are frequently used in metalworking, machining, and woodworking applications. Range / 0.037 inch to 24 inch, 1 mm to 608 mm Joint Type / Firm Maximum Measurement / 457 mm; 18 in Maximum Measurement - Inch / 18 inch Maximum Measurement - mm / 457 mm Minimum Measurement - Inch / 0.037 inch Minimum Measurement - mm / 1 mm Nut Type / Solid Caliper Material / Steel Leg Style / Flat