0.1mm thick aluminimum metal panels
Robustly painted metal corrugated panels on both sides.
The corrugations are spaced 2.5mm apart representing roofing sheets in OO/HO gauge or small corrugated metal panels in 1/32 and O gauge scales. 
Take a look at our 1.2mm corrugated metal page here
The more you buy, the more you save.  Price breaks available on all sizes.