The infill piece is actually straightforward and not a problem. Everything comes with the piece from Triumph. The more complex part is if you've removed the GT backrest and want to replace that with the metal strips (like on the R). That requires two purchases/part numbers - the metal top strips (2) and the brackets that install underneath and attached to the bike with fasteners. The top strips simply slide into the brackets. My dealer didn't know about the brackets and I had to wait for those to arrive after I already had the top strips.