They go from 4mm to 19mm according to Fluke - Not sure what the depth of the RCBOs involved are but that should be enough I would have thought.
They don't actually advertise them as GS38 Compliant, perhaps because they aren't spring loaded so wouldn't comply when retracted. However, that's no different to the older Megger ones with removeable covers. These are far more convenient because you don't immediately lose the covers...
It's surprising how often my old GS38 tips were defeated by a recessed choc block terminal..
They do them as whole test leads too, but I prefer to have the leads separate for a break out box.