Works as expected, haven't had any issues with it leaking. Great for the price!
My four port air pump is lower than the sponge filters. My three check valves still remain untested as my water fails to siphon over the top of the tank when turning off the air pump. I question if they are necessary. Three stars because I neither like nor dislike the product.
Feels like quality construction, it doesn't noticably inhibit air flow and they do stop water from siphoning out. I air leak tested 3 of these I am currently using in different conditions for the sake of leaving a review with some data. One had no air leaks, one had a barely detectible air leak, and one had a very noticable air leak. Ultimately the leaks were small and effectively this made no difference in my setups so I won't be looking to replace them and would buy again.
2 stars because of severe leakage. I bought the diffuser and check valve for co2 setup and zero bubbles made it to diffuser. All leaked out of check valve. However, I am using the check valves on my bubblers but I am concerned that if air gets out, water could too which would defeat the purpose of having a check valve.
Set this up to prevent backflow into my c02 regulator. Did a soap test right after setting up and there was a leak where the black base meets the clear chamber that leaked c02.