MR16 is a small reflector bulb, 2" across, sold on two bases that don’t swap. A GU5.3 base has two thin straight pins and runs on 12 volts through a transformer; a GU10 base twists in and runs on household 120 volts.
What it looks like
MR stands for multifaceted reflector, a small reflector bulb, and the 16 is its width in eighths of an inch. Check the pins on the old bulb or the code printed on it: GE’s specs name the 12 volt base “2-Pin (GU5.3)”.
Where it’s used
MR16s are used in track and accent lighting. The Feit GU5.3 MR16s below are listed for track, recessed or landscape lighting, and Feit designs its landscape ones for 12 volt fixtures.
12 volts and the transformer
A GU5.3 MR16 doesn’t run on standard line voltage. GE says its LED MR16s need a step-down transformer to 12 volts, either a magnetic or an electronic one.
Feit designs its LED MR16s to replace halogen MR16s in 12 volt fixtures, but says the transformer must be LED-compatible, and some older magnetic transformers may not work correctly with LEDs. Under ENERGY STAR’s rules, which ended for bulbs in 2024, an LED MR16 for low-voltage circuits had to say on its package that it works with low-voltage transformers, with a caution that it may not work with every one. Check the box for a line saying it works with low-voltage transformers.
If an LED MR16 flickers or doesn’t work properly on an old transformer, the transformer may not suit it. Changing a transformer means working on the fixture’s wiring, so leave that to an electrician.
On a dimmer
GE recommends trailing edge (RC) dimmers with electronic transformers for its LED MR16s, and doesn’t recommend them on dimming circuits with magnetic transformers. Lutron says its C·L dimmers aren’t made for low-voltage LEDs. More on flicker and buzzing: LEDs on dimmers.
The bulbs it comes in
| Bulb | Watts | Lumens | Dimmable |
|---|---|---|---|
| Feit LED | 6.6 | 500 | Yes |
| Feit LED | 4 | 300 | Yes |
| Feit LED, landscape | 6.4 | 550 | No |
| Feit halogen | 20 | 230 | Yes |
| GE LED | 6.5 | 530 | Yes |
| Westinghouse LED | 6.5 | 500 | Yes |
In order: Feit BPEXN/930CA/3, BPFMW/930CA, BPLVEXN/830CA/HDRP and BPBAB/CG/3/HDRP, GE Classic LED 50 Watt Replacement MR16, and Westinghouse 6.5MR16/LED/DIM/FL/30. All six are rated 12 volts.
Feit says its MR16 LEDs of 5 to 7 watts match a 50 watt halogen MR16, at about 400 to 500 lumens. For brightness, compare lumens on the boxes.
GU5.3 or GU10?
An MR16 with a GU10 base has short pins that push in and twist, and runs on 120 volts with no transformer. Feit and Westinghouse each sell MR16s on both bases, so the shape alone doesn’t tell you which you have.
MR11 is a smaller reflector, 1-3/8" across. Westinghouse’s catalog lists MR11s on GU4 and GU10 bases.
Switch the light off and let the bulb cool before you pull it out.
Another base?
Bases and shapes