It's not a retrofit of our frame, they are licensed to make them in the 21x24 and 23x32 sizes. They also feature welded corners instead of our extruded aluminum corners. It's also worth noting that they are the exclusive providers of fabric panels for those sizes.
That said, they are a major step up from the imitation frames that are out on the market right now - as much as I want to sway you to "our" EZ frame (available in any size you need) - the Solid-Loc frame is a solid option!