Zip files in one of three unique ways. 1) User-specified size [This method will create create something like "spanned zips" that any compression app (WinZip, WinRAR, etc) can do. However, the key difference with SpinZip is that the zips created are independent of one another unlike a normal spanned set where you need all the zips to extract the files.] 2) Number of files per zip 3) One file per automatically named zip.