L.R. Baggs Element Active System VTC Acoustic Pickup...

Common undersaddle pickups depend on string attack to directly compress
the sensors for their sound. This direct pressure is a root cause of the
infamous “quack”. In contrast, our patented Element derives output from
the movement of the soundboard and rejects string attack to minimize quack.
Its flexible film sensor, thin as a human hair, mirrors the soundboard’s
movement as you play to capture the guitar’s actual voice and its most
delicate nuances. In addition, the pickup’s minimalist construction
removes most of its influence on the acoustic properties, creates an
intimate coupling between the sensor and guitar for the highest fidelity
possible, and makes the Element amazingly reliable. Every pickup is made
here at our California factory and is pre-tested in a guitar for output
and balance.