PTFE provides added resistance to aggressive chemicals and temperatures versus a traditional rubber tube expansion joints. Our PRO231-xxx-ET are a rubber expansion joints like our standard PRO231 Spool, but they include a PTFE liner (which extends to the bottom of the bolt holes on the face of the flange). They provide an option for lower sound transmitting and dampening compared to metallic expansion joints, as well as reduce the chance of electrolysis when mating dissimilar metals. PRO231-xxx-ET come with an outer EPDM rubber cover and polyester tire cord fabric reinforcement, which can help it withstand tough, demanding applications. Available in sizes 1.5"-36", and normally 6", 8", or 10" lengths depending on the pipe size. Our PRO442-BD are reasonably priced expansion joints with a PTFE contour molded construction (2 bellows or convolutions/arches, no rubber). The flanges include a rust inhibitive primer to prevent corrosion and in sizes 1"-12" are typically ductile iron, and sizes 14"-24" come in zinc plated carbon steel (SS316, SS304, or Epoxy coated flanges also available on request). They also come with factory installed limit bolts to prevent over extension during operation (carbon steel bolt, nuts, washers and neoprene grommets). Available in sizes 1"-24", and normally 1.5" to 6" long depending on the pipe size. These PTFE joints are also available with 3 convolutions for greater movements and lengths (PRO443-BD), or 5 convolutions (PRO445-BD) in longer lengths or wider movements.