A CR123a battery is 16 mm long, 34 mm circumference and round, so it can also be called a 16340 (16 34 0). 16340 batteries can come in 3v, 3.6 or 3.7 v. So some sites will also refer to 3v CR123's and 3.7 CR123's. USUALLY a CR123 is not rechargeable - RCR123's are rechargeable, but some sites...