HTC has teamed up with Google to give selected smartphone owners up to 100GB of Google Drive storage absolutely free for two years. The offer applies to those with a One M8, Desire 816, and the Desire 610 — plus a number of popular devices that were launched last year. But there are some caveats.

The full list of eligible handsets — along with the amount of storage each one qualifies for — is as follows:

• One M8: +100GB for two years
• Desire 816: +100GB for two years
• Desire 610: +100GB for two years
• One max: +100GB for two years
• One M7: +25GB for two years*
• Butterfly S: +25GB for two years*
• One mini: +25GB for two years*
• Desire 601: +25GB for two years*

*These handsets are only eligible for free Google Drive storage after they have received a Sense 5+ or Sense 6 upgrade.

Google says that free storage must be redeemed by January 1, 2016, and it’s only available to those who purchased their handsets as new; used and refurbished devices do not qualify. What’s more, if you’ve unlocked your bootloader, you’re not entitled to anything, either.

To find out if you have free Drive storage, open up the Drive app on your HTC device and press the “Redeem” button.

• SourceGoogle