It's quite simple: A, B, C, E and S are the "normal" cars. SL is, well, the SL ("sporty and light", yes, seriously), and SLK is the little SL. CLK therefore is the SLK-sized coup?, ditch the K, and you have the big coup?: the CL. Mix coup? with S-class sedan, and you get a CLS.I can't keep Mercedes' naming convention straight. I don't know what's what.