MR16 light bulbs are commonly used in track lighting, recessed ceiling light fittings and display lighting.  They can be identified via the two small pointed pins they have as their base.  

The Difference Between White, Black, and Silver Backed MR16 Light Bulbs

Some MR16 bulbs will have a visible colour on the back as a means of identifying the type of material used to make the coating that has been applied to it.  This more often applies to halogen bulbs than it does for MR16 LED counterparts.

1. Silver Backed MR16 Bulbs (Dichroic Halogen)

Silver backed MR16 bulbs are the usual standard for dichroic halogen lamps.  These bulbs are made with halogen technology and they have dichroic reflectors which are designed to allow heat to pass through the back of the bulb and reflect light forward to keep the light fixture and surrounding area cooler.  It is believed that dispersing the heat behind the bulb and the light fixture will contribute to longer lifespan for the bulb and the fitting it has been placed in. 

2. White Backed MR16 Bulbs (Aluminium Reflector Halogen)

Non-dichroic halogen MR16S tend to feature a solid opaque white coating.  These types of MR16 bulbs use an aluminium reflector which traps heat and light directing it forward.  These MR16s bulbs do tend to run hotter than the silver backed dichroic versions so it is worth bearing this in mind when purchasing a halogen MR16 bulb.

3. Black Backed MR16 Bulbs (LED or Specialized Halogen)

A LED MR16 bulb will often have a black coating as this signifies the presence of a heat sink.  As LED bulbs generate heat at the base of the bulb heat needs to be directed away from the electronics as much as possible.  The body or the heat sink in an LED bulb will likely be made of anodized aluminium or a thermally conducted plastic to help with keeping the bulb cool.

It is worth mentioning that the backing colour is not a universal or legally required standard so it is important to always check the packaging and specifications listed on the bulb to ensure that you are purchasing the right one.

Can I replace MR16 halogen bulbs with LED?

Yes in most cases but you will need to pay close attention to the connected control gear and specifications required as below:

• Voltage: Mains voltage within the UK is 240v and standard MR16 bulbs operate at 12V and require a matching 12v transformer.  There are some LED versions which will be 220-240v not requiring a 12v transformer but this will be made clear on the packaging or website you are purchasing the bulb from.  
• Transformer Compatibility: You will need to consider the wattage of the bulbs you have and whether or not you will be dimming the lights.  For the wattage it is always better to go higher rather than lower and to match the total wattage for the number of bulbs that will be connected.  If it is dimmable you will also need a driver that allows for this and to make sure it is compatible with the same type of dimming as the bulb allows for and your dimmer switch. 

Are all MR16 bulbs the same size?

Yes, but there may be variations in diameter and length of the bulb itself.  The "MR16" designation refers to the diameter in eighths of an inch (16/8 = 2 inches, or 50 mm) and they all share the same GU5.3 base meaning that there are 5.3mm between the pins.  You may find that LED replacements may not be exactly the same size in the length or diameter of the body of the bulb so it is worth checking this before purchasing one.

Are MR16 bulbs being phased out?

Halogen technology is being phased out for them but the base form (i.e the pins/base) is not.  LED versions are being developed to replace the halogen versions. 

Halogen technology is steadily being phased out to increase energy efficiency for lighting fixtures.  With this in mind it is well worth looking into converting to LED versions.  As long as you make sure your connecting control gear is suitable for these bulbs and they will fit in your fixtures this should be a smooth transition.