http://www.gelpak.com/products/wf-film/?gclid=CKPD_JaLrMgCFarpcgodep8DwQ The most commonly used Gel-Film® product is the WF film which is Gel bonded to a metalized polyester substrate material which give a light grey appearance. WF is available with optional Pressure Sensitive Adhesive (PSA) backings ...