bip subframe
the mono sub frame is alloy (and some were prone to cracking at the exhaust hanger (warranty claim on older bikes!))
It isnt up to taking the load of 2 people therefore the Biposto subframe is made of steel tubing - you will also need the footrest hangers, the Biposto pillion seat and the plastics as there different as well. Its also handy to have another seat pad (usually on Flea bay) as you can leave it screwed to the Bip plastics rather than having to unscrew it off the Mono plastics all the time.
Put some copper slip grease on the subframe bolts as they arent designed to be unscrewed all the time if you keep changing from mono to bip.
Threaded Mode