During GIANT VOICE 1979, we had a presentation from a US flight surgeon about some fantastic new high altitude flying clothing he'd recently come across. It was practical and relatively comfortable, certainly more so than the pressure suits the USAF was then using.
It was the Mk21 regulator, P/Q mask and pressure jerkin AEA the RAF had been using for years........
He admitted then, that RAF research and development in the field of flying clothing was well ahead of the USAF's.