Fishing alarm batteries, if you have an alarm costing £30 or less and if it takes 1 small battery it will be this one, if you have Fox alarms that take two small batteries you will need LR1 batteries.

Duracell Specialty alkaline MN21 batteries – long lasting power for your devices. Duracell Specialty batteries have up to 5 years of in-storage guarantee with Duralock Power Preserve technology so you can be confident these alkaline batteries will be ready when you need them. They are designed for use in Wireless remote controls, wireless doorbells, security systems (alarms, locators).