Tartan. I had the tank installed by Facelift in Derbyshire, Heres their Email address.
http://www.faceliftcleaning.co.uk/gb/products.phpAll I can say is they have done a fantastic job with it. I wanted a Black tank similer to tucker poles without the price tag. I nearly bought a system from skypole but they did not do it in a stainless steel frame. Skypole said they could do it in stainless steel but it would cost.
Sometimes facelift do a competive package on smaller tanks about 400ltr.
They fix them in the van correctly, Phill one of the partners is an enginer and a perfectionist to boot.They fix specially desgined clamps underneath the van that go round your vehicle chassis. So if you have a collision over 30mph you know that the tank is not just going to rip the plates through the van floor.
Heres a pic of the plate.