Once cartridges are filled, it is not suggested to attempt to remove the mouthpiece for refilling of the vape cartridge. Special devices are used to apply the top mouthpiece, effectively sealing the tank to prevent leaks. Some companies have refillable cartridges, and while we love sustainability here at Bear Rootz we have not yet found a refillable cartridge that holds up to our standards and testing in order to offer them. We are always on the lookout for new, more sustainable products. Our 510 threaded cartridges are designed to be filled from the top and sealed by a press. The two different types of seals are push-lock and twist-on. Push-lock utilizes a locking mechanism that is snapped into place by applying pressure to the mouthpiece and cartridge. Once locked into place, they cannot be reopened or refilled. Twist-on designs are also locked into place by applying pressure, but by screwing the mouthpiece onto the tank. Some manufacturers apply a glue seal to effectively eliminate leakage while in use. Never force open a cartridge or break the locking mechanism to attempt a refill. This renders the vape cart faulty and can also contaminate the concentrate within.