SBC – small bayonet cap fitting takes a SBC bulb. Also known as B15d . Cap measures 15mm across.
BC – bayonet cap fitting takes a BC bulb. Also known as B22d. Cap measures 22mm across.
SES – small edison screw fitting takes a SES bulb. Also known as E14. Cap measures 14mm across.
ES – edison screw fitting takes an ES bulb. Also known as E27. Cap measures 27mm across.
GES – giant edison screw fitting takes a GES bulb. Also known as E40. Cap measures 40mm across.

Bulb_holder_types