Part number 81210051A is for a "nipple", a conical bush that joins the exhaust front pipes to each of the silencers, they were absent on my old 900 Monster and appear to be absent on my 888, the standard pipes were fitted without and sealed just fine, I have Silmotor hi-level pipes and whilst the mount points without these bushes don't align (the silencers sit too forwards in to the front pipes hence the fixed mount brackets miss the mount points on the sub frame) these seal fine as well (using straps to mount them)... I didn't realise these bushes exist until I studied a parts book, they aren't used for the SP5. They also appear to be quite 'fat' and may restrict... does everyone else use these on their Strada? Am I right in assuming that if I splash out a hefty £23 each my Silomotors will fit perfectly with the proper intended fixed brackets? The bush is no. 17 on this parts diagram - thanks!!