This twin pack of smoke alarms are by leading fire safety brand FireAngel. One of the smoke alarms features an ionising sensor whilst the other features an optical sensor and is less sensitive to cooking fumes including toasting. Easy installation, simply attach the back plate to the wall or ceiling, screw on the alarm and away you go. Both are cream and have a large stop/test button in the centre for ease of use. This product does not require batteries as it uses an internal power pack. This product has a warning alarm every time the power pack is getting low.