They list these clamps here and basically everywhere else as fitting 9/16" hose. While this may be true if you're fitting 9/16 hose to a larger barb fitting, it seems the closed size is 15.1mm or 19/32" therefore it WILL NOT clamp down 9/16" OD hose properly unless the hose is stretched over the fitting. Such is the case with most Gas line MFL's on quick connects. It seems you need a clamp that isn't offered here, the "157" clamp which has an open size of 15.7mm (5/8") and closed size of 13.2mm(17/32") Additionally, as the picture depicts this isn't a normal Oetiker clamp that has a band that covers the crimping location, which gives a slightly more even clamping pressure than the clamp here.
This clamp performs well so long as you have a large/thick barb inserted into a 9/16" OD hose. I have experienced some gas leaks with these clamps when using 9/16" OD hose with a smaller/thinner barb. If the barb is small, the clamp will not tighten enough to prevent a gas leak.