B&Q also do rolls of 2mm underlay. How does that differ (aside from 1mm)? Do you know? I cannot tell from their website. Would that be an alternative?
The 2mm foam appears to be supplied in rolls rather than concertina folds. No idea what else, if anything, might be different apart from the thickness.
I chose the 3mm because that's near enough ⅛", which I understand to be the best thickness for 00 gauge in terms of the shoulder height you end up with after ballasting. 2mm might give you a slightly mean-looking ballast bed.
I suppose 3mm should, all other things being equal, be better for sound deadening than 2mm. And it might keep the track a bit warmer...
Edited by ejstubbs, 15 November 2016 - 16:58 .