SIS - Symbian Installation File is a file extension that you can download online specially for Symbian OS. This is the type of operating system that is mainly used for mobile devices. You will also be able to create different command line tools with this program. This extension can be used for S60 phone themes installations. You have to have an SIS file in order for the file extension to work. You can also use the communication software associated with the extension and files as well. They really do make a big difference because there are different types of benefits that come along with them.