In reply to A Nidderdale boulderer.:
I can't remember exactly what rubber it is, but I find that Boreal Spiders stick really well to polished limestone (but not much else). It's quite a smooth feeling rubber compared to Stealth stuff but just seems to work.
I know this will be an unpopular opinion though as everyone slates boreal rubber.
I think the best rubber I ever had for grit was on some Scarpa slippers. They just seemed to stick to anything. I had been using C4 before that. Nothing else has ever come close.