This is a pretty simple Garmin mount specifically designed to mount as low as possible on a 90mm, +7° Bontrager RXL stem, although it will likely work for many other stems as well. It's a super sturdy mount and when my 520 is on there it's basically invisible. It's a little hard to see in the picture but there are 4 little feet on the bottom that are contoured to the stem to keep it secure.
My personal mount was printed in premium plastic and has been very durable so far. I can't say how well the basic plastic version would turn out.