SonicProtect for TZ300 FAMILY (TZ370, TZ370W) for 3 Years Equivalent of AGSS.
This is a subscription, and the licence extends your current TZ370 or TZ370 Wireless-AC appliance so you can later purchase one of the SonicWall TZ300 Family (next-gen - possibly called the TZ380?) via the Secure Upgrade (Appliance Only) with no Attached Subscription (Existing SonicWall Customers Only).
The TZ370 and TZ370 Wireless-AC are still current models.
More information: SonicProtect Subscription | SonicWall
Warranty & Support
3-Yrs hardware/3-Yrs support, firmware updates
Dynamic Support 24x7