I have seen several Ninja motors with OS plugs pissing fuel...they are not the correct taper.... you can torque a OS plug to seal but it can mess up the button if you ever go to run a Ninja plug again... Every manufacturer has a slightly different taper on their plugs...OS plugs will leak in both Ninja's and Picco's, tho I do know many people who manage to use them anyways....... When you thread an OS turbo in tight into the Ninja button you can see a gap between the plug and the button if you look from the underside, as if the plug is a little to short to fully fill the taper..... But before everyone jumps all over me I still have seen OS plugs used successfully in both Picco's and Ninja's...but I have also seen just as many needing to replace their head buttons because the OS plugs damaged the button when they tried to get it to seal...Fuel bubbling out around the dam plug no matter how tight they tightened it..... Safe bet IMHO is to match the plugs to the motor and be done with it.....