I tried a brand called "Knight" from eBay. Thought it was a great deal so I bought it, tried it and did't work.
Thought maybe they were bad, but I don't think they were.
Sent them back, got a refund.
Went to OWC and got what they specify, for my mac mini. 2 X 4GB , just like OWC says. everything checks out. I tripped check them.
Put them in and I still get the three beeps, then I put the old models in, works great. Tried it three times, with the same results.
This is what I found...
http://www.larryjordan.biz/caution-ssd-drives-and-yosemite/