From my extensive experience with metal cases, unless it is a hybrid that incorporates plastic or polycarbonate the signal is impacted significantly. Some case Manuf. like Element Case and Devilcase, with their Type X. do a good job of using metal and keeping signal strength. Draco Ducati is useable as are the Spigen and Verus Aluminum bumpers but even these last three will drop calls in low signal areas. This bumper that is uninterrupted Aluminum around the perimeter will drop one to two bars and calls, unless the signal is very good at a location.