I would call Jayco or visit a dealer with one on the lot and measure. Our previously owned Greyhawk and our currently owned Bungalow both have bunkhouses. None of the mattresses are the same size. The ones in the Greyhawk were very skinning, like 28" wide - compared to a normal twin that is 38" wide. We have 4 bunks in our Bungalow. The bottom bunks are 35" wide and the top bunks are about 30" wide. Most likely, your mattresses will be somewhere between 28" and 35"