An exhaust treatment device for treating exhaust comprising: a main body defining an interior , the main body interior extending along a longitudinal axis from a first closed end to a second end, the main body defining a circumferential wall extending between the first closed end and the second end, the circumferential wall defining an inlet opening towards the first closed end, the main body also defining an outlet ; an inlet arrangement disposed at the inlet opening , the inlet arrangement defining an inlet channel leading to the interior of the main body ; an aftertreatment substrate disposed within the interior of the main body between the inlet opening and the outlet , the aftertreatment substrate being spaced from the first closed end to define a mixing region within the main body interior; a restrictor arrangement disposed within the interior of the main body between the first closed end and the aftertreatment substrate , the restrictor arrangement separating the mixing region into a first chamber and a second chamber ; and a dosing arrangement configured to receive an injector to spray reactant into the exhaust so that the reactant mixes with the exhaust in the first chamber , the dosing arrangement being configured so that an injection axis of any injector mounted to the dosing arrangement is not coaxial with the longitudinal axis of the main body ; characterized in that the restrictor arrangement defines a restricted passageway between the first and second chambers , the restricted passageway extends into the first chamber towards the first closed end so that exhaust entering the main body interior from the inlet channel is swirled around the restricted passageway before entering the restricted passageway and passing to the second chamber ; wherein the first closed end is defined by an interior plate retaining insulation disposed within the main body . a main body defining an interior , the main body interior extending along a longitudinal axis from a first closed end to a second end, the main body defining a circumferential wall extending between the first closed end and the second end, the circumferential wall defining an inlet opening towards the first closed end, the main body also defining an outlet ; an inlet arrangement disposed at the inlet opening , the inlet arrangement defining an inlet channel leading to the interior of the main body ; an aftertreatment substrate disposed within the interior of the main body between the inlet opening and the outlet , the aftertreatment substrate being spaced from the first closed end to define a mixing region within the main body interior; a restrictor arrangement disposed within the interior of the main body between the first closed end and the aftertreatment substrate , the restrictor arrangement separating the mixing region into a first chamber and a second chamber ; and a dosing arrangement configured to receive an injector to spray reactant into the exhaust so that the reactant mixes with the exhaust in the first chamber , the dosing arrangement being configured so that an injection axis of any injector mounted to the dosing arrangement is not coaxial with the longitudinal axis of the main body ; <EOS>