I have bought a few variants of those and they all leak. Also they are too easy to knock out of adjustment. Only one I have found any good is a brass colour with a penny sized adjustment wheel. Been trying to work out where I got it from.
That brass one is also the same as what Machine Mart sell. I might look to get that JTB supplies one as I wiped my dial with thinners after it got overspray on and now its gone milky.