Replacement check valves

With all the recent post on plumbing upgrades and check valve failures, I have done some research and shopping trying to see what is available.

I found 2 that simply splice onto any section of PEX. 1 is from sharkbite and can be found here:

http://www.sharkbiteplumbing.com/sharkbite-u2008-check-valve

The other is from Watts and is here:

http://www.watts.com/pro/_productsFull.asp?catId=71&parCat=444&pid=3660&ref=2

I also found this nice small 1/2 NPT in-line valve:

https://www.makariosrv.com/products/Back-Flow-Preventer.html

If you all have found other post a link here. I have not been able to find any spring loaded valves locally.

Hopefully, this will help others in the future.

Good info Alan, Thanks!

Since the ones we have have a spring inside---do they have to have a certain pressure or are they all the same---just prevent backflow of water.
al