A reconstitution assembly includes a housing including a lower sleeve and an upper sleeve, including a first container and a second container disposed vertically opposite the first container. A transfer set assembly is disposed within the housing between the first container and the second container. The transfer set assembly includes an upper spike housing and a lower spike housing, with a flow path defined through the upper spike housing and the lower spike housing. The transfer set assembly is configured to access contents of the first container and then upon the activation of a triggering mechanism, create a fluid pathway between the first container and the second container. The triggering mechanism includes trigger fingers which ensure the transfer set assembly sequentially accesses the contents of the first container before accessing the contents of the second container. The disposition of the first container activates the triggering mechanism.