The 71-3270 K&E Scale Level holds Optical Tooling Scales from 3" to 20" and allows the operator to mount the scales vertically or horizontally. Using the bullseye bubble vials, accuracy of the vertical or horizontal can be set to within 15 seconds of arc per 2mm of movement. This unit was made by both Keuffel & Esser and Cubic Precision, and now Brunson makes the replacement unit- the model 563.