The remodeled BP-50a Oztec Backpack Concrete Vibrator has added a sealed rotary throttle that prevents fresh concrete from entering and seizing the throttle. The rotary throttle also ensures that the unit produces the proper vibration rate by eliminating the operator's variable setting of the engine speed. The vibrator handles heads up to 2½ inches, which develop up to 12,000 vpm. Oztec Industries Inc. 800-533-9055.