Often referred to as 2D, DD double turn or butterfly light bulbs, these energy efficient compact fluorescent CFL light bulbs are commonly used with low profile decorative and tough exterior luminaires in both domestic and commercial applications.The unique shape of these CFL 2D light bulbs provides even light distribution, while boasting an impressive a rated life of 10,000 hours and a typical lifespan of 5 years. This Crompton 28W 4 Pin Double D light bulb emits 2,700 lumens of warm white light and is perfect for use in offices, bathrooms and stairwells.Suitable for dimming - separate ballast/control gear required.Fitted with a GR10q 4-pin square push fit base. Need more help in choosing a suitable light bulb? Read our guide Choosing Compact Fluorescent Lamps