Abstract: The invention relates to an intra-ruminal device comprising a cap, with outlet, that overlaps a portion of the barrel to define an attachment zone. Located within the attachment zone is at least one protrusion providing a localised point of contact between the barrel wall and the internal sidewall of the cap to provide for an ultrasonic weld between the barrel and the cap. Optionally the plunger comprises at least one aperture to allow fluid or gas communication between first and second compartments in the barrel. Optionally included are at least one pair of resilient wings, each pair of wings having a pair of reinforcement ridge that extend a first distance from the body along the wing surface, and at least one middle reinforcement ridge that extends between the pair of ridges from the body a second distance, and where the second distance is less than the first distance.