For a very long time 5.10 didn't seem to know which rubber it was going to be. I saw samples with pretty much every possible option.
The production pair I just got seem to have HF on them. Dave, I am almost ashamed to say that 'wackblings' are much better than I expected. Not convinced they're better than Dragons but not bad.
I was never a Jet7 owner but they are at least superficially similar to Jet7 but they're very soft - much softer than I remember Jet7s being, although I could be miss-remembering Jet7s.
HTH, Iain