How to Identify Different Types of LED Bulbs
A practical guide to identifying common LED bulb types by base, connector, lamp form factor, voltage and physical dimensions — for wholesale buyers, distributors and everyday users.
Start with the Lamp Base
The fastest way to identify an LED bulb is usually to check its base. Two lamps may look similar, but a different connector can determine whether the product fits the fixture at all.
Two straight pins
4 mm pin spacing. Common in chandeliers, cabinet lighting and compact decorative fixtures.
Wider bi-pin base
8 mm pin spacing. Often found in under-cabinet and other specialty lighting applications.
Loop-pin contacts
Recognizable by its loop-shaped wire contacts rather than the straight pins used on many G-series lamps.
Twist-lock connection
Two short locking studs. Common in spotlights, track lights and recessed/downlight applications.
Small Edison screw
The number refers to the nominal diameter of the threaded screw base in millimeters.
Standard Edison screw
A widely used screw-base format for residential and commercial general lighting.
In G-series bases, the number often relates to contact spacing. In E-series bases, the number refers to the nominal diameter of the Edison screw base.
Do Not Confuse Lamp Shape with Lamp Base
This is one of the most common sourcing mistakes. MR11, MR16 and AR111 describe reflector-lamp form factors, not the electrical base itself. Always verify the actual connector before ordering.
MR11
Approx. Ø35 mm. Commonly paired with a GU4 base in compact low-voltage spotlight applications.
MR16
Approx. Ø50 mm. Depending on the product, an MR16 lamp may use GU5.3 or GU10.
AR111
Approx. Ø111 mm. Commonly available with a G53 base for larger accent and display lighting.
A GU5.3 MR16 and a GU10 MR16 may share a similar reflector diameter while using different connectors and electrical systems. “MR16” alone is therefore not a complete purchasing specification.
Check the Voltage Before Ordering
The lamp base does not automatically determine the operating voltage. Many G4 and GU5.3 products are used in low-voltage systems, while G9, GU10, E14 and E27 products are often offered for mains-voltage applications. Exact ratings vary by product and market.
For wholesale purchasing, confirm the input voltage, AC/DC compatibility, wattage, dimming function and driver requirements before approving an order.
Compare the Physical Dimensions
LED replacements can be larger than traditional halogen lamps because they may contain LED packages, PCBs, drivers and heat-management components. Always verify overall length, diameter, base dimensions and the available fixture space.
This is especially important for chandeliers, compact glass shades, cabinet lights and decorative fixtures, where internal clearance may be limited.
A Simple LED Identification Checklist
Before requesting a quote or placing a bulk order, confirm these five points:
Final Tip for Buyers
Avoid sending only a general model name such as “MR16” or “G4”. A complete inquiry helps suppliers identify the correct product faster and reduces unnecessary sampling or compatibility issues.
For distributors and project buyers, a clear specification sheet is one of the simplest ways to improve sourcing efficiency, reduce errors and make supplier quotations easier to compare.
