Configurable aftertreatment systems including a housing

An aftertreatment system for treating constituents of an exhaust gas includes: a housing defining a first internal volume and a second internal volume; an oxidation catalyst in the first internal volume and extending along a first axis, the oxidation catalyst configured to receive at least a portion of the exhaust gas via an inlet conduit fluidly coupled to the oxidation catalyst; a filter in the first internal volume and extending along a second axis parallel to and offset from the first axis, wherein an outlet of the filter is disposed within the second internal volume and configured to emit the exhaust gas into the second internal volume; at least one selective catalytic reduction (SCR) catalyst in the second internal volume and extending along a third axis that is perpendicular to the first axis; and a decomposition tube in the second internal volume in a direction parallel to the third axis.