This grinder has a serrated Teflon® pestle that disperses homogenate into the mortar cylinder more efficiently. These units are precisely constructed with completely interchangeable parts, allowing for easier replacement of parts so you don't need to keep pieces matched during cleaning. Grinding chamber clearance is .004 to .006 inch (0.1 to 0.15 mm). The unit can be autoclaved. Depth of the serrations is .020 to .025 inch. Diameter of the stainless steel shaft is 0.25 (6.3 mm).