Feit Electric 18-Watt Equivalent PL CFLNI Quad Tube 4-Pin G24Q-2 Base Compact Fluorescent CFL Light Bulb, Soft White 2700K (1-Bulb) BPPLD18E/HDRP - The Home Depot
NaturaLED 18W LED PL Bulb, Direct Line Voltage, 4-Pin, G24q/GX24q Base, 4000K (NaturaLED LED18PL/H/185L/4P/840/IF) | HomElectrical.com
Replacement for MAXLITE 18/27 G24Q-2 Light Bulb by Technical Precision - Amazon.com
PL Retrofit Lamps
2-Pin & 4-Pin Plug In Lamps Go LED — 1000Bulbs Blog
Maxlite L18T8SE415 102185 Photonmax Horticulture LED T8 Grow Light 18W