CR1220 Lithium battery and holder Size 12.5 x 2 mm 3 Volts Great for powering the leds in vehicles that you wish keep mobile and not hardwired to the layout I have fitted one these to a Morris police van OO gauge it powers the super chip and a blue LED on the roof. It ran the unit 10 days and was on 24/7 in normal use it last ages. Check the price Maplins price just the cell 2.29 Halfords 3.49
