one of several 3 courses in Motocross. 1. The 125 class 2. The 250 Class 3. The Open Class. Possibly the most well known class......Basically the number suggests the total amount of CC your bike i expected to need to participate inside competition. Just a few years ago people decided it was alright to race 400cc 4-stroke bikes into the 250 class against 250cc 2-stroke bikes. A 250 4-stroke does not have any possibility against a 250 2-stroke.....so i suppose this is reasonable. 1st 400cc 4-strokes performed effectively contrary to the 250 2-strokes plus it nearly evened thing up (powerwise)......but then Motocross Committee performed one thing stupid and allowed the 4-strokes 50cc much more........and now the 2-strokes are actually underpowered and no one races all of them any longer.So basically the 250 class has become the 450 course............They should simply call-it the Open Class, this way we could see a 500cc 2-stroke beat the crap away from a 450 4-stroke.