OH N 500 ECFThis is a TwinPack deal. You'll receive two (2) bulbs. The Original HN Sunlight OH N 500 ECF is a high quality bulb made with the finest raw materials. It is designed to provide high actinic output and long service life. The optimized spectral output guarantees rapid curing and short exposure times with the industries best dot to dot quality. The 108. 5 mm long OH N 500 ECF has a typical lifetime of 600 hours. optimized spectral output short exposure