In reply to Joe Miller:
I've just been and checked this out Joe, and because the 'biner is longer than average, the holding loop of most belay devices (I had a look with a Verso, a Bug and a VC Pro) is about 1/2 an inch away from the inner gate when using it normally.
Something with an extra massive holding loop like a Mega Jul could potentially get caught in the gate, but I wouldn't recommend one of these for use with a Mega Jul anyway as they work best with completely round HMS krabs.