... ,CUL, CE,TUV,approved HPSMH compatible No fans inside, digital electronic ballast 1000w. Welthink WEX120 and WEX230 digital ballast are designed ... hang the lamp, no need any external starter and compensation capacitor.Completely silent: no more humming and buzzing.Constant output of ... light soluaitons are available . UL,CUL,CE,TUV certificated digital electronic ballast 1000w,600w,400w,250w