Bilstein 5100

I'm new to the site so I apologize if this is covered elsewhere. I have had these on my truck for several years, front and rear, and I just had some work done on the front end. The mechanic was looking at the rear shocks and told me that one of them is the wrong part. The left and right have different part numbers and one is longer than the other. Upon research from the vendor who sold them to me and the Bilstein site, this is correct per Bilstein - they sell two different lengths for the rears. The mechanic said they should be the same and I do notice the back end will slam down when going over speed bumps occasionally. Anyone have any insight on this? Why would one shock be longer than the other? Thanks in advance.

 

Bilstein makes a standard travel and an extended travel version of the shocks. It sounds like you have one of each.