A device for singulating open-ended caps includes: a housing configured to retain a plurality of open-ended caps, the housing having an open lower end; an outer ring positioned below the housing; a drum fixed to and positioned within the outer ring to form a drum assembly, the drum including a hub having a substantially circular wall and a platform that extends radially outwardly from the wall to contact the outer ring, the hub and outer ring forming a circular gap therebetween, the platform being positioned below much of the gap and including a discontinuity; a mounting structure with an exit aperture fixed relative to the housing; and a rotary drive unit mounted to the drum that rotates the drum assembly about an axis of rotation.