The CBDFive cartridge (.5ml and 1ml) is a patented product, unlike other cartridge, it does not have a center tube inside the chamber. Its unique design makes filling cbd oil easily prevents oil from leaking as well as getting the utmost out of CBD oil.
Pre-filled CBD cartridges are expensive so I turn to fill empty cartridges with CBD oil, which saves me money. The empty cartridges works well, though I am not using it to CBDFive battery. Works fine, carts are compatible with the 510 thread battery. These are one of the best quality carts I 've ever had.