Always keep a replacement nozzle handy with your airbrush should you encounter nozzle damage during routine use, cleaning or maintenance. A nozzle can be ruined if your needle is hooked or bent inside it from accidental damage, or dropping of the airbrush.
A nozzle can also become scored or flared out of shape over time from needle damage and wear, or using a needle that is beyond it's normal service. The airbrush will no longer operate properly, such as "spitting" of pigment or inconsistent fluid flow.
Nozzles should be replaced periodically, and along with a new needle with it when the nozzle is replaced. Use the nozzle wrench that came exclusively with your SA-35 airbrush to properly remove and replace the nozzle without damage to the delicate threading. Be careful not to over tighten the nozzle with the wrench, or you can permanently strip out the threading.