Horticultural Growlights are the most important piece of equipment in the Growroom. High Intensity Discharge (HID) lamps for Growlights come in 3 types: High Pressure Sodium (HPS) have all the Red (Autumn) light for flowering crops, but they must always be Nav-T SUPER or Son-T PLUS or equivalent. Metal Halide are now used really only in the Vegetative stages - lots of Blue (Springtime) light for healthy green shoots. Metal Halides are perhaps not needed for those on a budget as HPS lamps have Blue light too. Grolux horticultural lamps are a mix of about 30% blue and 75% red giving a slightly higher output than an HPS lamp. A horticultural Growlight should not be confused with Hi-Bay or Lo-Bay lights which are designed for car parks,security lighting,street lighting etc. Hi/ Lo Bay lights are designed to produce enough light for us to see by but not for plants to flower with and are made for economy elecric use. A proper Growlight is geared differently to a Lo/ Hi Bay to force a higher light output from the bulb (trying to recreate Sunlight on a small scale) not with economy but RESULTS in mind. Our Growlights all take HPS and Grolux lamps and most take Metal Halide also.