Not sure why but all the labeling on this is backwards. On the screw top to change the filter the arrows are labeled backwards. It shows the arrow pointing to the left as ON. that's off in reality, also the inlet and outlet are also backwards. water should enter on the large side of the filter and exit through the center of the filter. On this filter housing the inlet goes to the center of the filter. Never seen one like this before. Beyond that it works good so far. I'm using this on a koi pond of 2500 gallons. you cold only see about a foot in the water after 2 hours we could see the bottom clearly. very happy so far. Only gave 4 stars for the poor quality control.