A ReFill is a kind of component package for Reason that can contain patches, samples, REX files and Song files. On your computer, ReFills appear as large files with the extension ".rfl". Storing audio samples in a Refill will significantly reduce the size of the files, with no loss of audio quality. The advantages of ReFills are obvious; third party manufacturers can produce downloadable sample collections for Reason for example, and it simplifies exchanging samples in general.

Samples (Wave and AIFF files) are compressed to about half their original file size when stored in ReFills. With ReFill Packer, you can "pack" patches, samples, Song files etc., into one self-contained file. In Reason, you can use the browser to list and access the embedded sounds and other components within the ReFills. just as if the ReFills were folders on your hard disk.

Where can I get ReFills?
 
ReFills are available from a lot of places including Dolphin Music. Most companies who make, sell or distribute samples make their samples available in ReFill format. The Propellerhead produced ReFills Strings (a high quality collection of live played strings) and Reason Drum Kits (an extensive library of life-like, multisampled drum kits) are also available.
 
How can I make ReFills?
 
The ReFill Packer

To create your own ReFills, you need the ReFill Packer. It lets you build ReFill files for sharing samples, loops and synth patches with other users.