The switch is brake light related. The aftermarket rearsets use a presue/banjo bolt rather than the usual pressure switch. Lightech send a banjo pressure switch with their rearsets. I think Gilles do also but not sure. The others don't send a banjo so you'll need to order one.
For the $10 I'd check off yes. I've had the displeasure of trying to adapt an OEM switch to work with aftermarket rear sets. The pressure banjo's are around $25 so $10 for an optional switch is good. It'll save you head aches installing.
That being said.....if this is a race bike, I wouldn't worry about the switch.
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