6100 and 6105 are about the same 7ft of reach and a 2ft flow diameter. 6200 had a roughly 6.5 ft reach and 2.5 ft diameter of flow, of course in narrower tanks this channeled for a longer reach. 6205 is about 5.5ft reach and 3ft diameter flow. Again, this will channel and reach further if a tank is not quite that wide. 6205 is better for shorter, wider tanks, 6105 is better for longer narrower tanks.