Halogen 12v MR16 spotlights are one of the most common types of lamp found in the UK. They are frequently used in downlights and various types of spotlight in domestic and business applications. Halogen 12v MR16 are 12v power supply fed by mains 240v through an external transformer. The fascia diameter is 50mm and they are installed by a pushing the GU5.3 pins into the holder. They are supported by a retaining clip held in by the fitting on the face.