High performance Li-ion Rechargeable Battery NITECORE 18650 batteries offer 50% higher capacity than non-rechargeable CR123 cells and are ideal for those who wish to save money on replacement batteries. These pay for themselves after a few recharges. The cells feature an over-discharge protection circuit and are custom-designed to withstand the high current demands of LED torches and other products. For safety and performance TorchMonster highly recommends the use of NITECORE cells as opposed to cheaper unbranded alternatives. These batteries are twice the length of the CR123. You can use a single 18650 instead of two CR123s. Advantage: They are rechargeable Disadvantage: They cost more initially, but pay for themselves as soon as you re-use them.