The iBeam’s MIPA award-winning design employs a matched pair of virtually weightless film sensors that flex with the soundboard to trace your guitar’s voice much like diaphragms in a stereo mic. A key advantage over typical bridge plate sensors is the iBeam’s “cardioid” like response pattern that inhibits feedback and string squeak while selectively admitting rich tone-producting vibrations. Weighing less than 1/3 of an ounce, the pickup will not alter the guitar’s natural acoustics and easily mounts to the bridge plate with peel-and-stick adhesive.

http://www.lrbaggs.com/sites/default/files/pdf/ibeam_active_manual.pdf