In reply to Prof. Outdoors:
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> If you do get one make sure that you wear it as designed. Snug but not tight which makes sure the heat is retained next to you. Must be worn next to the skin for maximum effect.
Which almost nobody ever does, from what I'v seen. Given how snug the fit was meant to be, and yet how the material is non-stretch, I could never use one for any climbing that was remotely technical - just too restrictive.
Also too warm, as I run hot. I wore one on attempted traverse of the Cuillin many years ago, got an unseasonably hot 26C July day and nearly boiled to death. And yet, despite their warmth, I could never get around to taking one on an expedition as they're not flexible enough - too hot for most days in Himalaya/Karakoram, not waterproof, bulky…
I wore my Special 6 shirt out eventually, but deliberately chose not to replace it.