Looks like they are almost the same, but not exactly. Pictures taken with the head from my murnan ninja mr12, a brand new ninja c7 plug and a brand new novarossi c5tf plug.





Ninja plug:



Nova plug:



The ninja plug seems to sit a bit lower and it also has a different shape then the nova. The tapers seem to be the same angle, but the nova seems to have a bit more of it, causing it to stick out a bit compared to the ninja. The ninjas shape looks like it would help a bit with igniting fuel, maybe smooth out the flow. Looks like you can use the nova, but it is _NOT_ the same and I have no idea how it would change the motors performance, and it probably does in some way.