thats the can bus controller motor but what most ppl dont realise is different frames need off set sprockets otherwise it screws up the chain line and will eat the cassette and chain in no time.
my new cx motor is smaller than the performance one so the off set is now 2.5mm so use a spacer that i got from peter as with 12spd it cant be wrong.
a haibke x sync sprocket for my bike at 20t is 100 quid fook that
