Weed membrane - roll size

Hope this is the right place to post this query. Apologies, mods, if not.

To business:

A friend has offered to bring over a roll of weed membrane for me. I'm thinking of something like this in 1 metre by 50 metres or 100 metres:

http://www.amazon.co.uk/gp/product/B000XT374O/ref=pe_1021161_62838331_em_1p_11_ti

The length of the roll is obviously about 1 metre (allowing for packaging) but does anyone know roughly what kind of diameter it would be? I've asked on Amazon, but the friend will be setting off soon and who knows when I'll get a reply. Any vague idea is better than none.

Thanks.

Thanks, Cadalot. Information forwarded so I hope they'll be able to bring it. It costs an arm and a leg here.

From memory my 100M rolls are about a foot in diameter.  (Some widths are folded double, on the cardboard core, I think??  If so they will be twice the diameter, less the diameter of the cardboard core, I suppose?)