Random Orbit Action. Researched and Deveolped for Ultra-Fine Finishing. Flex-cover gives comfortable grip, prevents stiff fingers. Low profile, vibration-free motor insures full contact sanding. Unique Air Efficiency System. Positive- Action Drive supported by 4-special bearings generates more power on less air. Over-size Drive Head eliminates pad-wobble for full contact sanding. New positive air control valve. Built-in pad release feature. model 4500H comes with 6" hookit pad. #1839 Handle avialable seperately. Replacement Pads: 5136 STD. 6" PSA 5236 Opt. 6" Hookit 5135 Opt. 5" PSA 5235 Opt. 5" Hookit 5108 Opt. 8" PSA 5108H Opt. 8" Hookit Other Specifications: RPM: 10000+ Wt. 3 Lbs 5 oz. Air Consumption: 9.8 cfm @90 PSI PSI Noise Level: 79 dBa