Usenet Nutter explained :
I had thought of Pipe Insulation but I think the stuff above might be
denser than pipe insulation and grey seems to be the norm for the pipe
stuff and also it is split and I'd prefer it without a split

Most seem only to be partially split, a thumb needs to be run down it
to get it to split completely - that is so it can be slid along the
pipe without splitting it, should you need to.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk