Future large optics systems currently under consideration require the availability of mirrors much larger than have previously been demonstrated. Taking a 4-meter diameter as a representative size for large monolithic mirrors, we will consider three material classes and their limitations to fabrication in volume. The materials considered are ceramics, metals, and advanced composites. After surveying currently demonstrated capabilities, we will project two years into the future to determine the potential production rate for the various materials, as well as identifying developmental limitations which must be addressed. Our purpose in writing this paper is to identify process and facility improvements required for each mirror type, along with alternate fabrication processes. That way, while planning future systems requirements, these long lead items can be kept firmly in mind.