Flat field quality optics without chromatic or spherical aberration. Measuring teticle is removable and is provided in the lens for microscopic measuring operations. Field diameter at 20x is 9/32inches with a 15/16 inch working distance. At 40x the field diameter is 9/64 inches with a working distance of 25/32nd inch. Reticle scale is 0-50. Reticle increments at 20x is .004 inch; at 40x is .002 inch.