The 51621 Rat Adaptor is included with all Lab Standard™ Stereotaxic Instruments. It has 30 mm of vertical travel along dovetail slide and 0.1 mm vernier scales. 50 mm of Anterior-Posterior travel possible. The nose clamp assembly, and either standard 18 deg. (traditional) Ear Bars or non-puncture 45° Ear Bars, are included. For nontraumatic ear bars select the 45° option (51620).