Strathmore 500 Series Bristol vellum 4 ply 23 in. x 29 in. sheet Plate surface has an ultra-smooth finish that is unsurpassed for detailed work with technical pen&#44; Vellum surface has a toothy finish that is excellent for pencil&#44; charcoal&#44; pastel and oil pastel 100&#37; Cotton. Acid Free. Size - 23 x 29 in.