PROFESSIONAL DESIGN: All-welded steel frames with powerful roller chain drives and pillow blocks featuring permanently sealed ball bearings for efficient operation PRECISE CONTROL: Variable roller speed selection from 20 to 300 RPM enabled by totally enclosed 1/4-HP DC motors and solid-state controls VERSATILE CAPACITY: Accepts two or three jars simultaneously for increased grinding capability compared to standard one-tier mills CONVENIENT ADJUSTMENT: Self-centering rollers easily adjust to fit various jar diameters without requiring clamping or fastening DURABLE CONSTRUCTION: Chemical-resistant rollers feature long-wearing design and resistance to static buildup