Hard plastic that breaks easily and is difficult to replace on a 300RR. The second one broke in less than a year. In 25 yrs of riding I have never bent or broken an aluminum subframe. What's more all the wiring for the RR, the battery box, air box, lighting etc. is integrated so it takes 2 hours of painstaking work to remove and install a new one. Sorry Beta but this really is the worst thing about the bike.
A little tricky to install rear signals. I watched their installation video but did it differently and easier. Basically drill the mounting stud hole drill through both side rails so you can access the stud with an Allen wrench from the inside. Then thread the stud from the inside side rail through the nut in the side rails and into the turn signal. Basically feed the mounting stud from the inside to the outside instead of from the outside in like the video shows. Once the stud is seated in the turn signal, tighten the mounting nut. Much easier and secure