B12 is a battery storage box, it could store up to 6 pieces 16340 batteries or CR123 batteries.
Specifications:
Outside diameter: 71mm/ 2.79in
High: 50mm/ 1.97in
Weight: 57.5g/ 2.03oz
Material: Polycarbonate
Storage: 6 x 16340 Li-ion batteries
More details!
