[Delphinus]

ANSI M57 is 175W probe start halide. H39 is 175W mercury vapor. I don't know about all 175W ballasts are like this, but I've noticed that all my 175W ballasts are both M57 and H39.

The only potential gotcha is that a lot of bulbs these days run better on pulse-start ballasts which are M137 for 175W. I run my Ushio's on M59's because that's what I have, done this for like 4-5 years now, but this year with the new set of bulbs I'm using I am starting to have issues where the lights don't ignite right away. Sometimes they light right away but other times they can take anywhere from 1 minute to 15 minutes or worse to ignite and stay lit. It's a minor nuisance, the lights do light up eventually, but it's something I plan to address somewhere in the long-term (either switching to a different light combo or at elast upgrading the ballasts if nothing else). Pulse-starts will be easier on the bulbs, hopefully improving their longevity, supposedly they are a little better too but I don't know how they "truly" compare in terms of intensity and power consumption.

I don't know why this year is different from previous years. I never had problems getting my previous lamps to ignite. Maybe my ballasts are getting old or maybe bulbs are getting more fussy; or maybe I was just lucky before and didn't know it. I didn't even know there was such thing as "pulse start" before a year or two ago.

Basically, if that's what you got, there's nothing wrong to use them, but when you decide what bulb to use, read the specifications carefully and if the recommended ballast is M137 then be aware you might have issues getting the lights to start.