Meinl Percussion TS-C-02 7-Inch Head for CS400, FWB400, and FFB400 Bongos Hand-selected True Skin Cow head Fits 8.5" Free Ride (FFB400), Free Ride (FWB400), and Free Ride Collection (CS400) series bongos Head is measured bearing edge to bearing edge. This is commonly referred to as playing surface.