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Light Bulb Base Types

Take a look at our handy guide to the different types of light bulb bases that apply to many incandescent and halogen bulb base sizes and types. Click on any of the illustrations to view all of the bulbs of that type offered on If you don't see the bulb you're looking for in the list, give us a call at 800.867.2852. We'd be happy to help you locate the correct light bulb. Halogen Light Bulb Base Visual Guide E10 Miniature Screw Base Bulbs E11 Miniature Candelabra Base Bulbs E26 Skirted Medium Base Bulbs E26 Medium Screw Base Bulbs RSC/R7s Recessed Single Contact Base Bulbs G4 2-pin Base Bulbs G6.35/GX6.35/GY6.35 2-pin Base Bulbs GU4/GZ4 2-pin Base Bulbs GU5.3/GX5.3/GY5.3 2-pin Base Bulbs GX9.5/GY9.5/GZ9.5 2-pin Base Bulbs G9 2 Contact Wire Loop Base Bulbs GU10 Twist Lock Base Bulbs B15d/BA15d Double Contact Bayonet Base Bulbs B15s/BA15s Single Contact Bayonet Base Bulbs Screw Terminal Base Bulbs GX16d Mogule End Prong Base Bulbs Medium Side Prong Base Bulbs G53 Base Bulbs

Decoding Edison Bulb Base Types

There are hundreds of unique bases for light bulbs. The most familiar is the Edison screw base found on most incandescent bulbs and many halogen, compact fluorescent, HID and now LED bulbs.

The common terms are medium, intermediate, candelabra and mogul. However, because the light industry likes mysterious codes, you may also see E26, E12, E39, etc. E obviously is for Edison. The number after the E is the diameter of the base in millimeters.

Here are the most common Edison base codes.

  • Medium (think household 60W bulbs) = E26
  • Intermediate = E17
  • Candelabra = E12
  • Mini Candelabra = E11
  • Miniature = E10
  • Midget = E5

The large Mogul bases found on higher wattage incandescent and HID bulbs are E39.

Most Edison base bulbs are called "single contact" because there is one contact button at the center of the base. However a few are called "double contact" (two buttons) in which case the designation becomes E26d or E39d.

The good news is there are relatively few Edison base designations. It really gets crazy with pin-based bulbs - there are well over 75 different types!