A REX file is a file that is created by or uses the Propellerheads Recycle format. They are notated by a .rex suffix as a tag to the file name, which is why they are commonly known as a REX files. They can be read by several different software programs other than Recycle. REX files are sliced in Recycle (or possibly other software) so that time and pitch can be more easily manipulated without artifacts. The math that Propellerheads uses to do this does an effective job so manufacturers such as Emagic and others have started integrating the ability to read the REX file format into their software samplers for playback purposes.