Thetford 135 a spare from my Monty 15 , the base is 13.5 by 11.5 inches and willing to part for it for a reasonable offer PLUS shipping. So here is the story it was purchased when I learned that these would be gone and discontinued, this one is not new used one or twice or three times when I did not know which one to use in my boat for the season but its been garage stored since 2013 so if interested let me know if NOT its going to be used when I dry camp in my RV (yet to be purchased). I can send pictures so let me know and I would say it looks like a +9 in condition. Smiley ex Monty 15 # 616 Karen & Smiley Magoo252@comcast.net <mailto:Magoo252@comcast.net>