High-pressure Sodium bulbs are HID (High-intensity discharge) lights used in horticultural applications to mimic the Winter season sunlight. Due to the change in seasons and aspect, the Winter months predominantly receive a more red light and shorter daylight hours, which in turn encourages stem and/or flower production. High-Pressure Sodium bulbs emit are ideally used during the fruiting/blooming phase of any plant that fruits during the Winter months. 600w bulbs are capable of illuminating 1.2m x 1.2m.