There is no easy solution for rechargeable CR123 substitute, Do not directly replace CR123 Batteriers with 16340. It is necessary to investigate the equipment for what voltage it can handle. CR123 Batteries is 3.0V while 16340 is 3.7V. Normal CR123 batteries have higher amp compare to 16340. NOTE: New battery must be fully charge before use The voltage of full charge and cut-off discharge is 4.2V and 2.75V. Don't heat, incinerate or reverse polarity. Please do not over discharge the battery . Specifications: Size:about: 33.5*16*16mm Net weight: 16g Color: Blue