A flow collar for use on a dual rod drill rod assembly includes an uphole end defined in part by a first interior portion having a first interior diameter and a downhole end defined in part by a second interior portion having a second interior diameter that is larger than the first interior diameter. The flow collar further includes a plurality of radially-extending peripheral fluid passages extending through the flow collar to the second interior portion. An outer rod interfacing surface defines a continuous annular surface with a constant outer diameter.