250 watt metal halide bulb type

Ok I just got a 250 watt hydrofarm Metal Halide Light system, and I want to get a new bulb for it. It says use only M58 type lamp, whihc I am unsure wat type that is, can I use any 250watt mogul base bulb or wat? Also any suggestions on a good bulb for vegging. This will complete my setup, i...