Ultra Alkaline are high performance batteries that are specifically designed for use in high drain devices. They give a very long operational life in portable electronic devices with high energy demand such as toys, games, digital keyboards and radios and will provide reliable, long lasting service in battery powered devices that are in constant use, like security systems or smoke alarms.Suitable for Microphones.These single use alkaline batteries have a voltage of 9V and a capacity of 630mAh. They are square in shape, with a height of 48.8mm, a width of 26mm and a depth of 16.9mm. They come in a box of four and have a shelf life of up to seven years.GP Batteries are known for their commitment to the environment and although GP 9V 6LR61 PP3 Ultra Alkaline batteries are not rechargeable, their high performance means that they will last far longer than standard batteries before needing to be discarded.