Light Bulbs: The Base
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When selecting or replacing a light bulb it is important to know the correct base otherwise the bulb won't fit in the fixture socket. The guide below does not cover every light bulb base available, only the most common ones found in fixtures in today's homes. Also, there may be many bulb shapes not shown that have similar bases.

Incandescent Light Bulbs
Medium	Candelabra	Bayonnet	Mogul
Most common screw base for household light bulbs. Table and floor lamps, ceiling fixtures, flood and spot lights	Smaller screw bases, regular and mini-candelabra. Common in chandeliers and some outdoor post lamps.	This base, with 1 or 2 contacts on the bottom, is inserted in the socket by pushing and twisting the bulb until it locks.	Uncommon - might be found in garage or utility building fixtures requiring high wattage bulb.
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Halogen Light Bulbs
Medium	2-Pin
Most common base for halogen household light bulbs. Sometimes used in recessed ceiling fixtures.	This is the type of base found in projector bulbs. Also used in low voltage track and cable lighting systems.
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Compact Fluorescent (CFL) Light Bulbs
Medium	Pin Base
Most common base for CFL household light bulbs. Can be substituted for incandescent bulbs in table lamps and other fixtures with medium base sockets.	There are many pin configurations for CFLs. Best to talk to the vendor before buying. Found in some wall sconces and step lights.
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Linear Fluorescent Light Bulbs
Bi-Pin
Single Pin