20lb. Solventless 100% Rag Vellum. Summit Medias Vellums are formulated for optimum imaging quality and reliable transport properties through your equipment. They exhibit excellent drafting characteristics as well as exceptional strength and durability for repeated handling. Dietzgen vellums can be used to create high quality, archivable intermediates that will not yellow or fade. Weight 20lb. Opacity -50% Caliper - 3.2mil (100 Sheets per pack)