My 640 has a 2-1/8" barrel. I think they all do, but I could be wrong. The 642 is 1/4 shorter (1-7/8"). Other than the barrel length, all of the J frames will fit the same holsters. My two kydex holsters from Alabama Holster Co and Theis Holsters fit both the 640 and 642 (and my 638 and 36). They were just ordered as "J frame" holsters. I didn't have to specify the model when ordering. These holsters have open ends at the muzzle. I had a leather holster that was custom made for the shorter 642. It didn't work with the 640 since it has a nearly closed end. I sold it and ordered another leather holster made for the longer 640 and now use that one for all of my J frames. That extra 1/4" of leather at the end of the holster is unnoticeable.Does anyone know if holsters for the 640 will work with the 642? I know they are both J frames but wasnt sure if they are compatible or not. I'm new to revolvers and got a 642 and see a lot of holsters for the 640 so was wondering.