Scratch that last question, the prop adapter is the same part for both the 1.5 and 1.2m versions. You need an 8mm hole to fit a prop on to that adapter. The prop should have come with adapter rings, one of which should fit snugly onto your prop adapter. Then you can either ream the prop at 8mm (5/16 is close) or a tad larger if you use the adapter ring.