I guess there are a couple of choices for the "dry" system besides the Pett. Reliance makes two types, a cheap $20 toilet seat lid and cover that sits on a standard 5 Gal. paint bucket, and a $40 "hassock" model that actually has an inner pail and an inner cover (that holds a roll of tp) plus seat and outer cover. Reliance also makes a fold-to-go tripod model for about $30, but the Pett looks more durable. Point being, these could also use the Pett bag system and/or there are similar reliance companion water-free products such as the Bio-Gel and what Reliance calls "Double-Doodie". All will show up on a Google search. I'm not where my boat is at the moment but I'm betting the 5 Gal bucket is too tall to fit in the M15 well but the Hassock is 14' tall and probably will. Also Coleman makes a hassock-like product with the same tp roll holder. I think what it comes down to with the Hassock or the Pett is whether the tripod with the bag hanging down below or a set of concentric cylinders (with the bag contained within) would be better AND which would be more stable for--as someone put it--"finishing the job." Upon further thought I'm leaning toward the Hassock, using the Pett W.A.G. bags and save myself $40. Anyone out there have any experience with the Reliance products? And thanks again Rik for bringing the waterless solution to my attention. Definitely the way to go. Neil