A flow guide configured for insertion in a cavity defined between an outer housing and a nested inner motor housing of a fluid driven tool and a tool incorporating the same. The flow guide has a longitudinal axis and includes at least two longitudinal portions disposed parallel to the longitudinal axis and defining longitudinal channel therebetween. At least one substantially circumferential rib portion connects the at least two longitudinal portions at points defining a plane substantially transverse to the longitudinal axis. A portion of the at least one rib portion located in the longitudinal channel has a thickness less than a width of the cavity surrounding the rib to define a circumferential recess that permits fluid communication in the longitudinal channel across the at least one rib. Also provided is a fluid driven tool having an outer housing and an inner motor housing nested in the outer housing and defining a cavity therebetween. The cavity has a first end with a first exhaust passageway and a second end with a second exhaust passageway. The inner motor housing has a motor chamber with at least one inlet port for a fluid driven motor and a fluid inlet, and an inlet manifold disposed in the cavity. The inlet manifold has a recessed portion with a surrounding seal configured to engage the inner motor housing and connect the fluid inlet to the at least one inlet port of the inner motor housing. Also provided is a fluid driven tool having an outer housing and an inner motor housing nested in the outer housing. An inner surface of the outer housing and an outer surface of the inner motor housing have portions that mate upon nesting the inner motor housing in the outer housing and provide reinforced areas for clamping regions of the outer housing located over the reinforced areas.