In reply to RR:
I can vouch for both the old style Pocket Rocket and the Reactor, as I've used it with both.
In recent years my Reactor has mainly been used as a kettle whilst car camping, but its relative instability isn't ideal, so the addition of the LowDown has been welcome. The fact that it also works for the Pocket Rocket is an added bonus, as it means I don't have to (rather unnecessarily) buy any more stoves!