Akrapovic Slip-On Race Line (Titanium) for Porsche 911 GT3 / GT3 Touring / GT3 RS (991)SO Slip OnSlip on system (S PO TI 15) for GT3 RS Speedster OPF model must be mandatory combined with: Evolution Header Set (E PO T 6 1) Tail pipe set TP T S 19. When combining the slip on system with optional carbon fibre diffuser DI PO CA 7 G, you must use tail pipe set TP T S 17. An additional original Porsche stock bracket (Porsche p n: 99111147391) is required for mounting the Akrapovi exhaust system. Please read the instructions carefully before