Tracking intrinsic and extrinsic vehicle parameters for optimizing vehicle performance is presented herein. Each cage bar has a roller guide face formed in each opposed face thereof, the opposed face being opposed to an outer peripheral face of a corresponding one of rollers. , product name and price, is clearly visible and associated with the product being merchandised. A pre-roll calculation program determines a pre-roll for each segment of the multimedia object and generates a modified multimedia object which includes a pre-roll for each of its segments, a pre-roll identifying a portion of the multimedia object to be transmitted by the streaming media server and received by the client computer prior to playback of the multimedia object at a selected segment. A shield mode is provided to prevent tasks from attaching to another task as child tasks.