Koppers System 2000 Modified Bitumen Membranes Koppers System 2000 series modified bitumen membranes offer a select group of specially compounded SBS and APP modified bitumen membranes. System 2000 membranes are available with either smooth or mineral surfaces. For more information on Koppers System 2000 Modified Bitumen Membranes, select from the following: Application Flashing Safety Measures  Return to Table of Contents