Hey! does this works for the G310R? or its only for the GS?There are 3 pieces involved:
#1 - the OEM BMW rear rack - if you have a GS, it came with the rack fitted. If you have an R, you will need to fit one - either buy it from BMW or find someone with a GS that wants the R's grab rails and swap.
#2 - the Givi SR5126 adapter. This bolts to the OEM rack and provides for mounting the M8 plate. It also additional support braces.
#3 - the Givi M8 plate. This mounts to the SR5126 and provides for mounting Monokey cases. There are cheaper plates than the M8, but I preferred the aluminum plate over a resin (plastic) plate. Note that I had a resin plate on my VStrom for 14 years and 95K miles with no issues - it's just a matter of aesthetics.
You could conceivably not use the SR5126, but you would have to make some adapter plate as the M8 needs to be raised a bit and the mounting holes don't match the BMW rear rack.