Large diameter c-axis crystal growth of sapphire boules up to 50 kg is in production at many sites worldwide. It has long been known that c-axis growth of sapphire could be the most cost-effective way to produce large diameter substrates for LED applications compared to a-axis growth with orthogonal coring due to the extremely large size boule required to core large diameter cores from the side of the boule. This paper will discuss the latest improvements, characterization, material utilizations, and crystal quality of boules designed specifically for 6-in., 8-in., and 10-in, wafer production. Improvements and continued R&D in slicing, polishing, and MOCVD of 6-in. and 8-in, sapphire has poised the industry for a rapid shift to larger diameter substrates, if the cores can be cost-effective. ARC Energy's CUES technology can produce 170 mm diameter boules optimized for 6-in. (150 mm) diameter wafer production. Additionally it can produce 8-in. or 10-in, diameter cores directly from 220 mm or 260 mm diameter boules, respectively. The latest developments, both equipment and process, will be discussed along with the resulting boule and core quality. Cost reductions for these large diameter cores will be shown to provide much more cost-effective 6-in. and 8-in. substrates. This low-cost enabling technology is poised to spur stable and long-term LED industry growth. (C) 2013 Elsevier B.V. All rights reserved.