it does not matter you thick fucking cock sucker,,,
get this in to your thick fucking head, if the ballast is for an hps bulb it will run a metal halide.
the metal halide ballast will not ignite an hps bulb.
switchable who gives a fuck, buy a basic magnetic hps ballast and put any fucking bub in it that is the same wattage.
a decent digital ballast will run any bulb up to 1000 watts !!!!!!!