They are awesome. Light weight, and do very well.
Normally their shipped with back heat, but with how its designed theres about 1/16th gap on bottom perfect for belly heat, which is what i have running in mine.
My sentec rack is no longer made as it was a prototype that uses abs plastic shelves. They now use PVC Foam board for the shelves. Its also enclosed compared to fully open. But im sure you can request either or.
Not to mention I live about 90 mins from Sentec so helps on shipping.