Drone killer extraordinaire!
Installed 2 on a 2017 F350 with a cat back full duel 3" exhaust (x-pipe, res delete, duel straight through mufflers). The exhaust was very loud on cold start and had a VERY loud annoying drone between 1500 and 2000 RPMs. The vehicle is used mainly for towing and the so the drone was going to be a deal breaker. These resonators significantly quieted the exhaust (cold start and acceleration) and eliminated 90+% of the drone. Installed after x pipe. Build quality appeared great. Would definitely recommend.