The Sigg Oval 0.6 Litre bottle that comes with the Canteen is stainless steel so is unlined. The outer is powdered coated so the neoprene cover is recommended as well.

http://www.amazon.co.uk/Sigg-Bottle-Insulation-Bottles-Neoprene/dp/B000OT23VQ/ref=pd_sim_sg_2

I believe that Sigg also do an identical Oval bottle in Aluminium so would be lined.

http://www.amazon.co.uk/gp/product/B001NPEMSM/ref=twister_dp_update?ie=UTF8&childASIN=B001NPCWG6

The combo Bottle+Mug item should always be stainless steel construction, but I would also check out the Tatonka Bottles as well. They are very lightweight for Stainless steel and fit perfectly into a Sigg Neoprene cover.

http://www.amazon.co.uk/Tatonka-Stainles...3163&sr=1-1

I also use a Smartube with the Tatonka Bottle in day pack side pockets as shown below

http://www.amfearliathmor.pwp.blueyonder.co.uk/CIMG0062eh.jpg