In reply to Wayne:
They look the part and have about 1cm of removable foam all way round ..except a strip down the middle as that is a velcro fastener.
Re: aconcagua I am not sure, they would certainly help and if youre lucky with the weather you could get away with it... but don't quote me on that ..if gets as cold as it reportedly can on occasions you may find you need to turn back on summit day ..and as its a pre-dawn start which doesn't exactly inspire warmth! Any more than than 1/2-1hr of properly numb feet and I am sure you know the consequences. Many people do go up in `normal' plastics but if you do wear them make sure the liners are always dry and buy some of those hand warmers as an instant heat source.
I will start the walk up the Horcones to base camp on the 24th Dec and must confess that the mule will be carrying a new pair of high altitude liners for my vegas...I have spent enough money on getting new high altude tent, duvet flight, permit, hotels etc I figured it wasn't worth the risk for an extra couple of hundred quid! ...I would be pissed if that is what prevented me from getting to the top (although it would have been a good excuse to cover lack of fitness and acclimatisation if I fail anyway!)
Just as a matter of interest when are you going?. I am there (with or without my mate who is still trying to get the time off work) from the 24th as mentioned above..
cheers steve-c