I have a Laars Mascot FT boiler. I would like to check the out pressure of the gas valve, but there is no spec for the size of the test ports. I measured the plug diameters at .1905", or almost 5mm. I am assuming that I can't just slip a neoprene tube over the test port, that I need something with a barb screwed into it? I've attached a couple of pictures of what I am talking about. Any advice that you can provide will be greatly appreciated. Thanks.

