FireAngel Optical Smoke Alarm with 10 Year Sealed For Life Battery, FA6620-R-T2 (ST-622 / ST-620 replacement, new gen) - Twin Pack , White : Amazon.co.uk: DIY & Tools
Replacement Alarm for FireAngel ST620 10 Year Sealed Battery Optical Smoke Alarm - UltraFire ULLS10 : Amazon.co.uk: DIY & Tools
FireAngel Smoke Alarm ST 620 : 4 Steps - Instructables