W211 Audio 20 fuse - 10amp or 15 amp?

[S-class]

Hi All

Was just wondering if anyone knew what amp the fuse is that drives the head unit on a W211 (2008 model), its a basic Audio 20.

I've tried to open the fusebox but appears to be stuck, was afraid of breaking a clip so was trying to avoid opening if anyone knows the info, doesnt appear to be in the car manuals.

Fuse is not blown, I'm planning an upgrade which requires 15amp.

Thanks