According to Perfecto, the only differences besides heights in some models is that they are not guaranteed to be water tight..........same thing with their reptile cases......they are made the same way but no warranty asd to water tightness is made........All I have ever seen is made with silicone sealant, and I sure can't tell one silicone from the other, and I have never really paid any attention to any silicone and have used whatever I had on hand when needed and its all worked just fine.........I have a 40 gal I made using GE Type I which is sold for sealing windows and doors etc and its been holding together just fine after 10 years of use...............