There are 2 versions to choose from when ordering the 2017 GSXR1000 bodywork
Quick release Tail & Hardmounted tail
These are the brackets for the Hard mounted tail, ie you bolt the tail on like most bodywork.
The reason these are needed is because there is a gap between the bodywork and the frame, These 4 aluminium spacers screw into the mounting holes in the subframe and they are drilled and tapped so you can then bolt your tail section to the bike.
When you order your kit these are offered at that time however you can always buy another set if you have a B bike or you loose them