I bought two of the #4's when they first came out (Feb maybe??). I really loved the flow and the easy mount magnets, however within the last month both of the pumps failed on me within weeks of one another. I don't know if there is a difference in the first ones produced but that is my experience. I since bought a Tunze 6045 to replace one of the Koralia's but I didn't feel that it really compares to the flow on the Koralia's. I then bought the mod kit sold for the Maxi jets and modded a 1200. Great powerhead, lots of flow, takes all of one minute to put the new propeller and case on the unit.........then viola! Of course you still don't have a better mount or magnet mount unless you buy that separate. I used the magnet from my Koralia (at least I could salvage something from the dead thing) and glued it on with a little Crazy glue. Great powerhead now!! I just thought I'd tell my experience for what it's worth.......