Ok, Dumb question time, I always lag my pipes wherever I have to with climaflex, however my local DIY shop has ARMAFLEX, this is black and is not slit so you would have to slide it onto the pipe before making any joints, the good thing about this is it can not fall off (or be pulled off).

What is the differance between climaflex and this armaflex???

as its a different material works a bit better but normally you cut it on the use there solvent to put back together What I tend to do for the uncut stuff is to slip it on first, this is a bit of a pain but it does mean that Mrs woman can't pull it off as soon as I leave to make her airing cupboard warmer. Armaflex works well on runs underfloors if using 10mm pipe on rads. Check the heat loss per metre to find out if one insulates better than the other.