An item processing arrangement transporting items at ;a prescribed nominal speed along a given transport track, with one or severed sort-pockets and associated diverters disposed therealong, whereby, in each sort-pocket, there is provided inject-reaction-guide arm assembly adapted to drive a so-diverted item into its pocket and comprising: an inject roll to accelerate and drive the item faster than this nominal speed; an arm assembly coupled to rotate with this inject roll and including a guide arm adapted to guide a so-injected item toward its position in the stack in the pocket; this inject roll and guide-arm being arranged to rotate the arm away from its stack each time an item is entering under the action of the the speed differential, and also arranged to be spring-driven to return the arm toward its the stack.