Zeno Acne Clearing Device Replacement Tip relies on carefully controlled heat doses in order to kill P. acnes bacteria. After multiple cycles of heating and cooling, treatment tips can degrade and become unable to reach sufficient temperature, reducing the efficacy of Zeno's therapy. Zeno's Treatment Tips are therefore limited in the number of treatment cycles they allow so as to ensure that the thermal efficiency cannot degrade to the point of preventing adequate treatment temperature. The Zeno Treatment Tip Cartridge has a memory chip to make sure the right amount of energy is given. It also controls the number of treatments, and makes sure the device is safe at all times. The Treatment Tip Cartridge that came with your Zeno allows 90 treatment cycles, as shown by the number on the top of the cartridge. Each treatment cycle is 2 1/2 minutes. Once the treatment cycles have been used, the Treatment Tip Cartridge must be replaced.