This OSRAM 28w 4pin 835 (standard white) 2D Lamp comes with a GR10q cap type fitting. This energy efficient compact fluorescent lamp has an average lamp life of 13,000 hours and has a Class A energy rating. 2D lamps are normally used in corridors and general bulkhead fitting applications normally found in supermarkets, hotels, schools, shops and public buildings. This 28w 4pin application is for high frequency control gear only, and will not work with switch start control gear. This 2D lamp is also known as a PL-Q, CFL square, Butterfly lamp and a Double D lamp.