The XL tank is the same as a standard tank, just longer.. Both tanks use the same stainless steel end caps. (mine and his). I read all the posts in this thread about the prepunched holes and self punched. TBH, it makes no difference in our issue. The carto will not fit in the end cap even at the very top. The deformed carto from self punching does not even come into play since it is punched at the bottom. The very top of the carto is still perfectly sound. Additionally, I've tried with a carto that wasn't punched at all just to see if another carto from the same 5pack would fit any better (it didn't).