A reagent container includes a base defining a plurality of wells having openings exposed at an upper surface of the base and a tube receptacle. The plurality of wells include a first set of wells and a second set of wells. Each well of the first set of wells has an opening to a well bore and a channel in communication with the well bore. The opening has a first portion disposed over the well bore and a second portion disposed over the channel. The first portion has a larger area than the second portion. An angle defined by tangents to the inner surface of the first and second portions at a junction between the first and second portions is at least 100° and not greater than 180°. The reagent container further includes a top coupled over the top surface of the base and defining windows providing access to the openings of the plurality of wells and the tube receptacle.