The most precise RGS Instruments ever made. Tolerances are less than 20 microns made of the finest quality steel with lightweight color-coded handles. Dr. Stevenson’s prep evaluation device will easily show you the ideal and maximum allowable extensions and pulpal depth of your class II preparations, and the incisal reduction of PFM preparations. The small end of the instrument measures 0.4 mm in diameter and 1.5 mm in length, and the larger end of the instrument measures 0.75 mm in diameter and 2.0 mm in length. Used by thousands of dentists, students and several dental schools, this guide serves to train your eye to within 0.1 mm of the ideal in your quest towards preparation mastery.