Pk2 Energizer Max 9V Batteries.
Energizer MAX© 9V Alkaline Batteries with zinc-manganese dioxide (Zn/MnO2) chemistry, no added mercury or cadmium.
They will hold power for up to 5 years in storage.
Typical applications include smoke alarms, carbon monoxide detectors and other moderate current drain devices.
Supplied in a pack of 2.