This read-write integer object specifies the Class of Service value defining a Weighted Fair Queuing group for this FlowPoint, grouping the flow's traffic under shared WFQ scheduling parameters distinct from the port-wide WFQ group settings. An administrator sets this to place a specific customer flow's traffic into a WFQ group whose excess-rate behavior is tuned via the related group EIR objects on this same FlowPoint. For example, assigning a particular COS value here lets an operator apply a distinct WFQ excess-rate policy to just this one flow point's traffic rather than to the whole port.