I guess you really can't tell but there is no adjustment on these. If it does not tighten up its useless. I was thinking the little one I made was to large. But the one I got from BDT was .010" bigger. I hope all the inlet and outlet barbs are all the same size. I can see this not working if the barb is too small. I am :thinking: ESR's barbs are on the big side.