Just put this nice pair together for a customer with an early 1966 N15CS. I’ve had a few NOS NLA “chopped” rights for years so nice to put one to good use. The LH float chamber serves both carbs. I had a pair on an AJS “33” in the late 1960’s and they worked well except with a sidecar fitted the right hand cylinder cut out on right hand bends. Also slide adjustment on the left hand carb is a bit of a pain!