While this grow light is advertised with 72-cell seed starting trays, it is much too narrow to work well. The single bulb reflector is only 3 1/2 inches wide so doesn't cover the ten inch width of a 72 cell seed starting tray. The 72 cell tray is six cells wide but the light only adequately covers three cells. The result is that the outside seedlings are leaning over to the center, trying to get enough light. They are spindly as a result. Don't buy this light if using 72 cell trays, but buy a wider light.