Foam. Rider seat 12" wide; passenger seat 8" wide. Unlike the regular Silhouette; which is a solo seat with an attachment for an occasional passenger only; the Silhouette 2-up comes with an actual; but subtle; passenger seating area. Perfect for cruising around town or maybe even a little further. The smooth rounded edges give the Silhouette its fluid custom look. Built to last with LePera''s ''Marathon'' high density one-piece poured foam on a black powder coated 16 gauge steel base plate; which is carpeted on the bottom and edged with a metal reinforced vinyl protectant. The upholstery is double stitched premium Naugahyde vinyl.