27A (also called A27 or MN27) 12V alkaline battery.These are small cylindrical 12-volt alkaline cells commonly used in:
Gate / garage door remote controls
Car key fobs
Alarm system remotes
Other small wireless transmitters
Key specs
Voltage: 12 V
Chemistry: Alkaline (primary, non-rechargeable)
Size: Approx. 28 mm long × 8 mm diameter