This is a copy of something I posted on Facebook.
I used Arimitsu 516 on all of my SS bays. I won't get into "This one is better than that one" because both make good pumps. I will say that the Cat 5CP-2120 is inferior to the 310 though. It's easier to work on, but in longevity, not so much. It does have the lifetime warranty on the original head, and you will eventually use it, because it will most likely wash out. A benefit of the Arimitsu is that it has 4 outlets as opposed to 2 on a Cat, which makes plumbing one up a cleaner job and also makes repairs easier. Never had a valve problem with an Arimitsu. I used them all (and also Gail), over the decades I spent in the business.
On a side note: On the Friday before July 4th, I had a 516 making a funny noise. It had been in place for 10 years and the oil had never been checked or changed. When the pump shut off, it was seized. There was no oil in it and magic smoke was wafting up from the fill hole. We didn't get a new pope that day, so I figured this pump was dead. I filled it with some air compressor oil because that was all I had, and stuck a crow bar through the pulley spokes and got it to turn, and loose enough to put back into service. I hoped it would make it through the holiday weekend and until I got a new pump. Well, I sold the wash to
Dakota Hoskins a couple of years ago and to my knowledge it still running. Oh, and did I mention that was July 4th weekend in 2015!