Axle shafts flanges or splines?

[PatricdeBoer]

I've been making calls around town to find some new axle shafts for my 81 300sd. I found a place that said they had two types that would work for my car. I couldn't understand the guy on the phone very much, but he said something about one having splines and the other having flanges. I've never dealt with axle shafts on any benz yet, so do either fit? There was a pretty huge price difference between the two.