An after-treatment system includes a Selective Catalytic Reduction (SCR) catalyst or a similar aftertreatment unit or brick that may be inserted into the opened end of a sleeve. The aftertreatment brick includes a substrate matrix with catalytic material that extends between a first face and a second face. A mantle is disposed around the substrate matrix and extends between a first rim proximate the first face and a second rim proximate the second face. The mantel may include a overhang extension that extends the first rim of the mantle beyond the first face of the substrate matrix. To enable retrieval of the SCR catalyst from the sleeve, a retrieval feature is disposed on a readily accessible, inner surface of the overhang extension.