-. SPEED CONTROLLABLE -. STEEL OR PLASTIC IMPELLER -. HIGH EFFICIENCY AND LOWER NOISE -. EXTERNAL ... , AIR CONTROLLING SYSTEM-. AIR COOLING AND HEATING UNIT, FAN FILTER UNITER, CLEAN ROOM, AIR CLEANER-. MOVING AIR ... COMUNICATION UNITO. MODEL NO.-. BOB-180/30-2P ; PLASTIC IMPELLER/ 2POLE-. BOB-190/45-2P, 2S ; STEEL OR ... 2,4 POLE-. BOB-225/50-2S,4S ; STEEL IMPELLER / 2, 4POLE-. BOB-250/50-2S,4S ; STEEL/ ...