A 400w HPS ballast requires a 400w HPS bulb. The only exception is a 400w MH conversion bulb, (converts your light from an HPS spectrum to a MH spectrum) but the 'regular' HPS bulb is better for all-around use, than the converaion bulbs.
Do not use any other bulbs in the HPS.

The price is good, if no replacemnent parts are required.