I'd take a guess and say it's called the Bulkhead End Cap, in the rear of the manual is titled as -
Rear Bulkhead Set ZS-300RT.
I googled manuals and found this place but it's been trying to download it for ages, nothing happening though ??? Maybe because I'm using a different browser to what it likes ???
http://www.competitionx.com/pdf/vehi...ial-manual.pdf