ballast vs bulbs

[davidbe]

Hi,

I bought some Plusrite bulbs over the internet (yeah I know they're not great bulbs but wanted to try anyway). Noticed afterward that they were for M80 ballast. My Outer Orbit has M138 ballasts.
Question is, can I run the bulbs on those ballasts safely? What is the difference between an M80 and an M138?

Thanks guys.
David