If you have a first-generation Apple Watch that’s faulty, you could bag a free upgrade when you take it to the Apple store.

Employees and Authorized Service Providers in some countries have been given authorization to replace original models with Apple Watch Series 1 units, but only certain variants are eligible.

Apple is now selling refurbished Apple Watch Series 1 and Series 2 models.

These devices aren’t outdated: They debuted back in September, when they got unveiled alongside the iPhone 7. You can find them cheaper if you buy them second-hand on eBay or Craigslist, but refurbished units from Apple offer a number of advantages.

Apple now sells two different versions of Apple Watch — Series 1, which starts at $269, and Series 2, which starts at $369. So, what’s the difference between these two models, and is Series 2 worth the additional $100? Find out right here.