MR16 Bulb
A compact multifaceted reflector bulb 2 inches in diameter, commonly used in track lighting, display cases, and landscape fixtures. Usually runs on 12V.
MR16 stands for multifaceted reflector, 16 eighths of an inch (2 inches / 50mm) in diameter. The "multifaceted" part refers to the dozens of small mirror facets inside the reflector that produce a smooth, even beam — originally developed for slide projectors, now ubiquitous in track lighting and display applications.
Most MR16 bulbs run on 12V and use a GU5.3 bi-pin base, which means they need a transformer. This is important when upgrading from halogen to LED: old magnetic transformers can cause flickering, buzzing, or incompatibility with LED MR16 bulbs. Electronic transformers work better, and many LED MR16s now include their own driver that tolerates both types.
There's also a mains-voltage version of the MR16 form factor that uses a GU10 twist-lock base — these are completely different electrically despite looking similar. Always check the base type and voltage before ordering replacements.
Specifications
| Diameter | 2 in (50mm) |
| Voltage | 12V (most common) or 120V |
| Common base | GU5.3 (12V) or GU10 (120V) |
Related Terms
- GU10 Base
A twist-and-lock spotlight base with two pins spaced 10mm apart. Runs on mains voltage (120V/240V) — no transformer needed.
- GU5.3 Base
A bi-pin base with two pins spaced 5.3mm apart, used for low-voltage (12V) MR16 spotlight bulbs. Requires a transformer.
- Low Voltage Lighting
Lighting systems that operate on 12V or 24V instead of mains voltage (120V/240V). Common in landscape lighting and LED strips — safer to install and requires a transformer.
Mentioned in
Can I Use A Halogen Transformer For LED Lights?
A single MR16 LED draws just 4–7 W, but most electronic halogen transformers demand a minimum 20–60 W load — and that mismatch is why your new bulb flickers or won't start.
Do LED Lights Work With Old Wiring? (How To + Diagram)
That MR16 spotlight flickering after a bulb swap isn't faulty wiring — it's the old halogen transformer rejecting a load it was never designed to handle.
What Does Low Voltage Lighting Mean?
Low voltage doesn't save energy — watts do, and older 12V halogen MR16 lamps ran at 50W or 75W each. The efficiency win you're thinking of comes from the LED, not the voltage.