Choosing Halogen Spotlights
The most common halogen spots are either push fit (GU4 or GU5.3), low voltage type or twist and lock (GU10) mains versions.
The PAR 16 (GU10)
The GU10 has two studs at the bottom and has a twist-lock action to insert and remove from the fitting. This measures 50mm across the face of the bulb. It is a 240V mains halogen and is quite different from the 12V versions. You may wonder what the 10 in GU10 stands for, it means that there is a 10mm distance between the centres of the two studs.
The MR16 (GU5.3)
The MR16 has 2 sharp pins on the bottom of the bulb and is simply a push fit into the fitting. This is a 12V lamp which requires a transformer and quite a bit larger than the MR11. It measures 50mm across the face of the bulb. The 5.3 in GU5.3 means that there is a distance of 5.3mm between the two pins.
The MR11 (GU4)
The MR11 has 2 sharp pins on the bottom of the bulb as well and is also a push fit into the fitting. It is a 12V lamp which requires a transformer, but what makes the difference between this and the MR16 is the width of the bulb. This measures 35mm across the face of the bulb. The 4 in GU4 means that there is a distance of 4mm between the two pins.
