The needle jet is the part the needle slides into. It is also the part the jet screws into from the bottom on a Bing. It has numbers on the side of it. This is the size of its internal diameter. Stay away from numbers with an A at the end. These are only for 2 position needles. And the orifice is sunk in a bit. I wouldn't want you to hang a throttle. Mopedwarehouse will probably have the 2.15 in stock. I checked Handybikes for you. I didn't see it there. Which suprises me a bit. Usually Handybikes has everything like that.