Several extra quality features can be enabled with custom firmware, including:

Primarily supports the 802.11n standard on the 2.4 GHz frequency. Connectivity: Includes one USB port and basic WAN/DSL functionality.

: There is no official "Extra Quality" tier of firmware. Firmware is either official (from the ISP/Sagemcom) or custom (OpenWrt/DD-WRT), though the 4315 has limited support for the latter. 3. Accessing Your Current Firmware

Most users looking for "extra quality" firmware are searching for ways to unlock hidden features or improve stability. However, the Sagemcom 4315 is largely a locked ecosystem ISP-Specific Locks

There is no official "Extra Quality" branch from Sagemcom. The term is used by power users on forums (DSLReports, Reddit, BroadbandReports) to describe non-standard or ISP-neutral firmware.