It is a small-medium beer 10 gallon batch maker at best.
I couldn't have said it better.
Have you tried high-gravity brewing with the 10 gallon round Rubbermaid cooler?
If your goal is 10 gallon batches with OG's >1.080, then you're talking 25 lbs or more of grain in a 10 gallon cooler. Then you will have the problems I'm talking about.
In the final analysis, I don't want my equipment restricting my options when it comes to the styles and recipes I brew. A large rectangular mash tun allows me to do step infusions, stir, and lauter quickly all types of beer styles from small to large gravities, including those with significant % of wheat. A round cooler does not.
Yeah, I call it doing 2 mashes
I don't recommend it for more than even 20 lbs of grain as efficiency takes a good dive for me. When I bought it I thought great for 5 gallons and can do 10 if I want in future. Silly me. But yeah limited types of ten gallons for sure. I have a 15 gallon stainless that I currently use for bigger beers >1.08 but want that 104 qt big boy rectangular cooler, love the simplicity.