Digital ballast. 1000W, 600W, 500W and 400W MH/HPS compatible , 120V/240Vconvertable UL,CUL, CE,TUV, listed No fans ... inside The features of the Welthink series Grow light ballast,digital ballast.Run for ... is option.Approval: UL,CUL, EMC, ROSH,CE,TUV. Suitable Bulbs250W, 400W, 600W, 1000W HPS/MH ... 34 in (135mm) UL,CUL, CE,TUV, listed 120-240V,1000W,600W,400W, digital ballast