Yep, as hoptob indicated, though K & L Frames share the same grip frame (same trigger reach), the L Frame has a bit more girth than the K, which is plainly obvious when holding them side-by-side.
Though my 686 fits my FIST #20 for a K Frame, I can tell that it would stretch it to the point of becoming useless for my K Frame Model 15. Best to spend the extra dough and get dedicated K and L frame holsters.