RR50 looks just like the standard one.
However that part is poorly located on the ST2 and so it's prone to overheat.
So I went for the RR51 which I have located in the air intake just underneath the headlight.
http://www.electrexworld.co.uk/rr51-...ier-737-0.html I think at the time I got the tip from the Desmotimes book. No problem whatsoever a couple of years later.