What WinZip offers to Windoowzz users, StuffItt does for MacOs users. If you started with StuffIt Deluxe 5.0 ,originally from Aladdin Systems, you can upgrade it. A free upgrade to 5.1.5 is available to registered users (have your serial# ready to instal). DropStuff and Expander version 6.0.x is available for PowerPC systems or higher. These upgrades are highly recommended if you experience problems with recently compressed files. They will coexist with your Stuffit Deluxe 5.1.5.