Standard Vibratory Feeders with a SpaceSaving Design and Easy Part Changeover. Performance Feeders' cap feeders are vibratory bowl feeders standardized to feed a wide variety of flattop caps. Using adjustable tooling and an air proximity sensor, they are capable of feeding caps from 1/2" to 11/2" diameter, and from 1/4" to 5/8" height.::: Situation:.