How many Horde levels are in Gears 2? Which one is the highest one you reached?

How many Horde levels are in Gears 2? Which one is the highest one you reached?

I believe there is about 50 levels in the Horde mode. The highest level I have ever reached is Level 25, and by then it is already quite difficult.

There are 50 levels

I have completed all 50 twice (for achievements) and up to certain levels on specific maps (also for achievements lol)

Its pretty fun when some friends and I have nothing else to play.