The world's largest sapphire boules up to 340-mm diameter are produced by the Heat Exchanger Method (HEM). In order to meet all applications, the highest purity crackle is used so the product has impurity levels very near the detectability limit of Glow Discharge Mass Spectroscopy (GDMS). The charge size of production 340-mm diameter sapphire boules was increased from 55-kg to 70-kg, and larger 380-mm diameter, 84-kg boules were produced. These boules were used to produce 315-mm diameter, 132-mm high sapphire cylinders to meet customer requirements. Efforts have been taken to produce a nearly flat top surface of HEM-grown boules with minimal undulations along the sidewalls to allow fabrication of larger sapphire pieces for production boules.