[Mullins]

They make a very thin, lightweight suit that seems to have a fleece inner and rubber outer. Handy for the tropics, but if you're wearing a suit that thin then using one made of compressible neoprene won't give you much of a buoyancy-change penalty anyway. I'm guessing this system isn't flexible enough for use on thick suits as their 5mm is still made of neoprene.