This is a replacement Battery pack or the Alrtair 2X Gas monitor. It can drastically cut costs of your gas detection requirements by extending the lifetime of your already purchased Altair 2X gas monitor. This comes as a pack of 8 so there are plenty of replacements available. Features and Benefits New replacement batteries extend the lifetime of your current gas monitors Pack of 8 so there are plenty of replacement batteries for your monitors Note It is recommended that a professional carries out this replacement to ensure correct installation.