Apple says that "under very rare circumstances" a crack can form along the rounded edge of the screen in aluminum Series 2 and Series 3 Apple Watch models, starting on one side of the screen and then continuing around it.
Customers with an eligible Apple Watch model can have their Apple Watch screen replaced free of charge from Apple or an Apple Authorized Service Provider if it is exhibiting this type of crack. Affected customers can contact Apple support for an email repair, visit an AASP, or visit an Apple retail store.
All Apple Watch Series 2 and Series 3 models in aluminum are included in the repair program, with a list available in Apple's support document.
Apple says the new program covers eligible aluminum Apple Watch Series 2 and Series 3 models whichever is longer than three years after the unit's first retail sale or one year after the program's launch date.