REFLEAK estimates composition changes of zeotropic mixtures in leak and recharge processes. The leak/recharge simulation program consists of three parts: 1) the pre-processing section for inputting required data, 2) the computation section which simulates leak/recharge processes and, 3) the post-processing section to display calculated results and to print or store data and graphs. Version 6.0 System Requirements: Personal computer capable of running Microsoft Windows 7, 8, 10 with Microsoft .NET Framework version 4.7.2 or later and Microsoft Visual C++ Runtime Library (for x86) version 14 or later; A hard disk with 17 megabytes of available space. The installation process will require additional 104 MB of space for Microsoft .NET Framework version 4.7.2 and Microsoft Visual C++ Runtime Library (for x86) version 14 if they are not installed already; The screen resolution should be set to 1024 x 768 or higher to view images in their entirety.