The Model 16B is an evolution of the TRS-80 Model II. It is a large cabinet which holds the computer, the monitor and a single sided full height Shugart 8 inch drive, which used single sided floppies with a capacity of 500K. (That was an enormous amount compared to the ~87K that was free on a Model I TRSDOS system disk.)
The system includes two CPU's - a Z80 for compatibility with the Model II, and a 68000. This allowed it to run Xenix, a form of Unix.