Agree with all points NVDucati made. I've had them for 3 years now. They are excellent "bang for the buck". Quite subdued burble at light throttle but they sound like my long departed air cooled Ducati SS under full throttle. They still polish up nicely, although the bike is garage kept and I only ride on dry days.
Downsides. Left side muffler blocks rear axle removal. Also, both mufflers block lower shock bolt removal. Mufflers fit very snug to head pipes; lots of wiggling during install and removal. Some smarter folks here probably know less tedious methods.
I've always wanted a 2 into 1 exhaust on the Interceptor, but these inexpensive mufflers just look so correct.