I have an EF model.
I like the filter. I got it used and had very few dollars to lose. It's larger than the Eheim Pro II that it is a knock off of, so it's heavier when full of water. It works great. Priming is actually easier than the Eheim, which I also have.
The major caution I have for any of the knock off filters, is the ceramic impeller shaft. There are, to the best of my knowledge, no sources of spares. The only substitute material I know of is drill rod. Which in forums - other than this one - is a major problem to overcome.
The second caution is that the quality of the plastic in knock off filters varies.