Apple will replace select Apple Watch units at no extra cost, according to its updated support document.

Those whose aluminum Series 2 or Series Apple Watch is suddenly cracking around the edges could be eligible for a free replacement.

In its support document, Apple notes that "under very rare circumstances," the displays on the models in question are developing cracks that can stretch along the rounded edges of the device.

Apple Watch Screen Replacement Program

If Apple determines that an affected Apple Watch unit is suffering from this just-discovered issue, it will grant a free screen replacement. Unfortunately, this is not the kind of repair folks from its Genius Bar can handle. So affected users will have to ship their device and wait for five days, perhaps more.

Another thing is that Apple is looking for very specific cracks: those that are located around the edges. As such, those who simply dropped their Apple Watch units aren't eligible for free screen replacements. Additionally, stainless steel and ceramic models that use a different display aren't covered. Nike+ models are included in the replacement program, though.

Apple is offering the free screen replacement program for three years after the first retail sale of the unit or one year from the start of the program, whichever is longer. This is not the first time Apple launched a replacement program for erring devices. Quality issues on some of its other devices, including the MacBook and iPhone, forced it to offer replacement parts at no extra cost.

How To Know If Your Apple Watch Is Covered

Feel free to check out Apple's support document for more details on eligible devices. But those who don't want to go through all the trouble can just check out the official list of eligible models below:

• Watch Series 2 sold between September 2016 and September 2017

• Watch Nike+ Series 2 sold between October 2016 and October 2017

• Watch Series 3 GPS and GPS+Cellular sold between September 2017 and September 2019

• Watch Nike+ Series 3 GPS and GPS+Cellular sold between October 2017 and September 2019.

Customers can either arrange to ship their affected unit by contacting Apple Support or walking into an Apple Authorized Service Provider or retail store. Again, the device will be shipped off to an Apple Repair Center instead of being fixed on-site, so expect to wait several days before getting it back and that's if Apple determines if the unit is eligible for the free replacement program.