Single Twin Tube bulb with a GX23 base Gives a warm white light Estimated life of 9.3 years based on 3 hours use per day Philips PL-S 13W/827/2P/ALTO (14681-1) Lamp Bulb Replacement PL-S 13W/827/2P/ALTO T-4 T4 T 4 T/4 13 watt (13w) 55 volt (55v) GX23 (2-Pin) 2700 kelvin Frosted BC1847 Order Codes: PL-S 13W/827/2P/ALTO PL-S13W/827/2P/ALTO 13W/827/2P/ALTOPL-S PL-S 13W8272PALTO PLS 13W/827/2P/ALTO PL-S/13W/827/2P/ALTO PL-S-13W/827/2P/ALTO PL-S 13W 827 2P ALTO PL-S 13W-827-2P-ALTO PL S 13W/827/2P/ALTO PL/S 13W/827/2P/ALTO Mfg Prod Code: 14681-1 146811 14681 1 14681/1