4 sheet is old UK sized bus shelter. There are still a number of these panels available on train stations and selected road side sites, although they are not as prominent as a few years ago. They represent great value for money for an outdoor campaign.
6 sheet 1800mm x 1200mm 72" x 48"
6 sheet This is the European sized bus shelter. Over the last few years the old 4 sheet have been superceded in a number of locations by 6 sheet. Most of these sites are back illuminated and therefore give 24 hour exposure.
16 sheet 120" x 80"
16 sheet mid sized outdoor posters based on 4 x 4 sheet giving a total advertising space of 120 inches high by 80 inches wide. Again, dependent on availability, these will give great value for money.
48 and 96 sheet the large format roadside billboards, made up of 12 and 24 x 4 sheet posters respectively. For a prominent, visual, striking campaign, this would be a good selection.