Product review (5 stars): Very easy to install
Fit our seven-year-old Whirlpool Duet Sport perfectly. Very easy to install. It now comes with a thicker o-ring in the box and you do need to replace it; we tried to be lazy, installed it as it came and it leaked. Took it back out, switched out the o-ring, and it works like a charm.  One note if you are not sure your drain pump is broken, take a flathead and pop off the end where the 'propeller' is.  There was a whole bunch of smelly thick sludge inside...we never tried the old pump again after cleaning it (we had already received the new one) but it is worth a try. Our pump was working intermittently- occasionally we would have a load make it through with no F-21, but usually we had to drain it manually. Wish we would have done this a long time ago. Another note: you do not need to tilt the washer back as suggested in many utube videos- I was able to get the front panel off without tilting it. I am not "handy," nor strong enough to tilt the washer back, and I didn't have the correct tools, but I was able to switch this out pretty easily. You can too. You need a little flathead or something to press down a tab on the old pump so you can twist it away from the drain basket too. That was the trickiest part.