The moore wright firm joint jenny calipers are manufactured from polished tool steel and have a large headed nut and screw assembly that provides a firm and rigid friction joint with no play the leg which holds the round adjustable hardened point is offset and model 341 has a locating spur on the straight leg the sizes listed are the effective leg length which is measured from the joint assembly note firm joint caliper capacities are generally 13 greater than the effective leg length