Flexible Circuit Technologies, Inc. has promoted these products / services:
Flexible printed circuits were originally designed as a replacement for traditional wire harnesses. From early applications during World War II to the present, growth and proliferation for flex circuits and flexible printed circuit boards continues exponentially. A flexible circuit in its purest form is a vast array of conductors bonded to a thin dielectric film.
A four-layer combination rigid flex circuit has four conductive copper layers. Typically, a four-layer has two flexible layers and two rigid layers.