From LR Baggs: 

The Award-winning Anthem series, featuring our patented TRU•MIC technology, seamlessly combines a proprietary condenser microphone with our acclaimed Element pickup to deliver the warmth and fidelity of a studio-mic’d guitar anywhere you perform. 

At the heart of the Anthem is a revolutionary microphone engineered to capture a dynamic studio-mic’d sound for any live performance. The TRU•MIC mounts to the underside of the bridge plate and hovers just 3 mm above its surface to take advantage of the PZM or “boundary” effect. This proprietary mounting system, combined with noise cancellation, frees the mic to perform as if it were outside of the guitar in a studio and maintain remarkable feedback suppression for the stage. The result is a balanced frequency response with excellent clarity for the purest sound you have ever heard amplified. We have paired the Element pickup with the TRU•MIC to provide solidity and punch for low frequencies.