The Brunson 160 Coordinate Micrometer- Dual Axis consists of two Optical Micrometers mounted precisely in one housing. Each drum measures +/- 0.100 with direct readouts at .001". The housing was made to fit Brunson Instruments with a diameter of 1.655", but Brunson makes a adapter- Part number 160-A- that allows this to be used on A.I.A. standard 2 1/4" instruments. This is in excellent condition, and comes in its original Brunson wooden box.