PROFLEX® RST (Rubber Seam Tape) is a 28 mil tape for seaming PROFLEX® underlayment membranes. PROFLEX® RST consists of a rubberized membrane laminated to a high-strength, reinforcing Mylar film on the face and a siliconized release sheet on the adhesive side. When used with PROFLEX® membranes, PROFLEX® RST will form a seamless, monolithic, sheet over the substrate.