Apple has launched a replacement program today for a “very small number” of 3TB hard drives sold within 27-inch iMac models from December 2012 to September 2013. The issue here is some of these drives “may fail under certain conditions,” says Apple.

Those affected by the issue should have been contacted by Apple if they provided an email during their product registration process.

Apple says they will replace any affected hard drives free of charge at their stores or any Apple Authorized Service Provider. You can check your eligibility by visiting the replacement program page here—all you have to do is enter your iMac’s serial number.

The program “covers affected iMac models until December 19, 2015 or three years from its original date of sale, whichever provides longer coverage for you.”