The present status of sp3 in the area of diamond growth using hot filament CVD is given. After a brief description of the deposition systems being used by sp3 and a discussion of selected applications of sp3's products, the paper focuses on why the hot filament technique was selected as the deposition technique of choice. Topics discussed include case of scaling, deposition system costs, Film growth rate and film uniformity, safety issues, and temperature and process control. Finally, the economics of hot filament reactors compared to other deposition types are discussed. (c) 2005 Elsevier B.V. All rights reserved.