A device for delivering a beneficial agent is provided and generally includes a cassette, a pump, and a delivery tube. The pump includes a pump housing containing a pump assembly having a fluid drive component. The pump housing has a receiving region disposed proximate the fluid drive component and further includes a rear closure portion. The rear closure portion includes a membrane disposed between the receiving region and the fluid drive component. The cassette includes a cassette housing, which has a cassette body region defining a fluid reservoir chamber therein. The cassette further includes a cassette base region having a boundary configured to be received by the receiving region.