Precision  drill bar or ''steam boat'' for you old school types. Square and parallel on all four sides so that in any orientation the hole for the bushing is square better than 0.0005'' one inch from the end of the bushing. There is a .100'' step under the sleeve for the drill bushing for chip clearance and to allow for drilling closer to the corner radius in pockets. Designed to accept 1/2'' OD slip fixed drill bushings up to 3/4'' long.