Exhaust gas aftertreatment device for an internal combustion engine, which at least partially removes pollutants from an exhaust gas stream of the internal combustion engine introduced via an inlet opening and then discharges said exhaust gas stream via an outlet opening, at least having a) a housing assembly comprising a1) an inlet housing shell having an inlet-side end at which the inlet opening is formed, and having a first receiving end at which a first receiving opening and a first radially outer mounting flange are formed, wherein the inlet-side end communicates with an interior of the inlet housing shell, and a2) an outlet housing shell having an outlet-side end at which the outlet opening is formed, and having a second receiving end at which a second receiving opening and a second radially outer mounting flange are formed, wherein the outlet-side end communicates with an interior of the outlet housing shell, b) a substrate assembly comprising a plurality of exhaust gas purification substrates bundled using a frame, wherein b1) the frame surrounds or encloses the bundled exhaust gas purification substrates as viewed in the circumferential direction, wherein a third radially outer mounting flange is formed on the frame, and wherein b2) the bundled exhaust gas purification substrates project on the one hand with first sections through the first receiving opening into the interior of the inlet housing shell and on the other hand with second sections through the second receiving opening into the interior of the outlet housing shell, wherein c) the first radially outer mounting flange, the second radially outer mounting flange and the third radially outer mounting flange are releasably connected to one another by connecting means in such a way that, on the one hand, the inlet housing shell is connected to the outlet housing shell and, on the other hand, the substrate assembly is held within the housing assembly, and wherein d) some of the bundled exhaust gas purification substrates each have at least one exhaust gas purification element and a jacket which encases the at least one exhaust gas purification element, characterised in that e) the jackets of at least some of the bundled exhaust gas purification substrates are in contact with one another and are connected to one another in a material-locking and/or form-fitting manner. a) a housing assembly comprising a1) an inlet housing shell having an inlet-side end at which the inlet opening is formed, and having a first receiving end at which a first receiving opening and a first radially outer mounting flange are formed, wherein the inlet-side end communicates with an interior of the inlet housing shell, and a2) an outlet housing shell having an outlet-side end at which the outlet opening is formed, and having a second receiving end at which a second receiving opening and a second radially outer mounting flange are formed, wherein the outlet-side end communicates with an interior of the outlet housing shell, a1) an inlet housing shell having an inlet-side end at which the inlet opening is formed, and having a first receiving end at which a first receiving opening and a first radially outer mounting flange are formed, wherein the inlet-side end communicates with an interior of the inlet housing shell, and a2) an outlet housing shell having an outlet-side end at which the outlet opening is formed, and having a second receiving end at which a second receiving opening and a second radially outer mounting flange are formed, wherein the outlet-side end communicates with an interior of the outlet housing shell, b) a substrate assembly comprising a plurality of exhaust gas purification substrates bundled using a frame, wherein b1) the frame surrounds or encloses the bundled exhaust gas purification substrates as viewed in the circumferential direction, wherein a third radially outer mounting flange is formed on the frame, and wherein b2) the bundled exhaust gas purification substrates project on the one hand with first sections through the first receiving opening into the interior of the inlet housing shell and on the other hand with second sections through the second receiving opening into the interior of the outlet housing shell, wherein b1) the frame surrounds or encloses the bundled exhaust gas purification substrates as viewed in the circumferential direction, wherein a third radially outer mounting flange is formed on the frame, and wherein b2) the bundled exhaust gas purification substrates project on the one hand with first sections through the first receiving opening into the interior of the inlet housing shell and on the other hand with second sections through the second receiving opening into the interior of the outlet housing shell, wherein c) the first radially outer mounting flange, the second radially outer mounting flange and the third radially outer mounting flange are releasably connected to one another by connecting means in such a way that, on the one hand, the inlet housing shell is connected to the outlet housing shell and, on the other hand, the substrate assembly is held within the housing assembly, and wherein d) some of the bundled exhaust gas purification substrates each have at least one exhaust gas purification element and a jacket which encases the at least one exhaust gas purification element, characterised in that e) the jackets of at least some of the bundled exhaust gas purification substrates are in contact with one another and are connected to one another in a material-locking and/or form-fitting manner.