Why doesn’t my cartridge screw on anymore?

The 510 thread on your battery can get stripped due to cross-threading or excessive tightening. To prevent this we recommend gently screwing-on your cartridge and making sure not to over tighten it.Unfortunately, if your threads have been damaged we will not send out a replacement due to user wear. Please get in touch with our customer care team if you do experience problems, and we'll help you out.