Product review (5 stars): Perfect
My reverse osmosis system was running water down the drain constantly. Since I wasn't exactly sure which part was bad, I decided to buy a new auto shut off valve and a new check valve. I replaced the check valve first and bingo! no more waste water running constantly.  Will save the ASO valve just in case it decides to go out later on down the road.
The product arrived in two days instead of the projected three which was nice too.