I think because Radium has the check valve in the baffle plate (theirs or the stock one) so same same.I'm just starting to look at the various catch cans on the market. I had a question about the check valves. The UPR catch can includes a check valve that goes in the line that feeds back into the intake manifold. I understand its purpose and get what it is there for, but I was wondering why some catch cans use one and others don't. Like I mentioned UPR is one that uses it. Radium however does not have a check valve in their catch can kit. Do any of you happen to know why some of the catch cans use one in the "out" line of the catch can and why some other catch cans don't have one in that line.