Does an MH conversion bulb fit every HPS ballast?

Look here: -http://htgsupply.com/viewproduct.asp?productID=47253

Says: " For use with 250 watt High Pressure Sodium Ballasts (S50 type) only."

Is this S50 type? -http://htgsupply.com/viewproduct.asp?productID=54182

Bump, I really need an answer

thats a digital ballast, i believe you can you run either a hps or mh in it no need for conversion bulbs.

ya u get a digital ballast with it to run the hps or mh you just have to make sure you buy one with interchangeable bulbs

I emailed them and they responded that the MH conversion does fit and so does a same watt MH in any of their digital ballasts

I still don't know what "S50" type means but it doesn't matter