[Delphinus]

There's no markings on the outside to indicate what ANSI rating the ballast is?

My guess is, you'd probably know if it was a pulse-start, they tend to be a tiny bit more cost-wise, so if it wasn't advertised as such when you bought it, it's probably a probe start.

Seems to me that every so often there's a sale on Radiums, that's basically the time to pick them up. I haven't really followed the prices of 400W lamps in the last few years since I haven't been using them. In the meantime try the XM's maybe. I *was* just about to suggest looking into the Venture bulbs, but never mind - I see they're about the same price as the Radiums nowadays (what the heck is up with that? There was a time they were *way* less expensive than the other lamps! I tried some Venture 250's last year coming off my Iwasaki's but coming off the Iwasaki's they were *way* too blue .. it like a discotheque in the basement kind of blue so to avoid culture shock I asked to exchange them for some XM's 10's instead).