just get a 400mh designed to burn in the position needed and you should be fine, example do not buy a bulb designed to burn base up and install it in a horizontal fixture or vice versa.
bejay Reviewed by bejay on . Need help figuring out which MH bulb to get! So when we got out HID system, we payed $50 and promised to smoke the guy up once. Not a bad deal. The hps ballast and light are being used, but the MH bulb burnt out when we first got the systems. So now I want to buy a replacement asap. The thing is I have no idea on the specs of these ballasts. I did some research, googled M400LU/HTL and found this website which had a spec sheet about the light which said S51 EYE Hortilux Metal Ace So then here I am on 400 Watt Metal Halide Rating: 5