Po 220 / Po 350 / Po 500 Disc Bore Φ25mm Or Φ36mm Center Hole. 2. Po 220 / Po 350 / Po 500 Adopt Worm Gear Transmission Design Moving Without Any Gap. 3. Control: Can Control Forward / Reverse, Manual / Automatic, Test / Weld Functions. 4. Stepless Speed Adjusting System , M-Type With Timer Setting , N â Type With Keeping Setting , L â Type With Hand Position Setting .