OZTEC FS21OZ 21 ft. Flexible Concrete Vibrator Shaft with . OZTEC FS21OZ 21 ft. Flexible Concrete Vibrator Shaft with Quick Disconnect Coupler inner core is made from extrahigh carbon steel wires with casings made from tough abrasion resistant neoprene rubber, reinforced with multiple layers of high tensile wire braiding with a hardened flat steel liner.