23A (also called A23, MN21, 8LR932, or V23GA) 12 V alkaline battery.
This is the standard battery type used in many car key fobs / remote keyless entry transmitters, as well as some garage-door openers, wireless doorbells, and similar small RF devices.
Key specs (typical for the batteries shown)
Voltage: 12 V
Chemistry: Alkaline (primary / non-rechargeable)
Size: Approx. 10.3 mm diameter × 28.5 mm length (slightly taller/thinner than an AAA)
Construction: Usually 8 small LR932 cells stacked in series inside a single outer can
Common capacity: ~40–55 mAh