SODIUM LAMPS 50 Watts ES (E27) base Eliptical shape Coated glass Internal ignitor (ignitor is contained within the lamp) Some lamps will have either an I (Internal) or E (External) inside a triangle printed on the lamp to indicate whether the lamp has an ignitor or not. Please see below for some of the different manufacturer names for these lamps: GE- LUCALOX SYLVANIA- NAV OSRAM- VIALOX PHILIPS- SON