the conversion bulbs is use are SOLARMAX and allow me to get MH preformance from a 600W digi ballast it was very handy as i couldnt hang another fixture in my veg area but i knew i needed more light. when you shop for bulbs go th the manuf spec sheet and they will give you all the info you need MOST of the bulbs are exclusively designed for our type of cultivation its a matter of tweekin and you aint there yet try a HORTILUX HPS 600W bulb for flowering