Guides and tensions roller chain within a drive run, carrying the chain load through an integrated sprocket mounted on a bearing unit. Bore diameter is 25.0 mm, outside diameter 52.0 mm, and the unit weighs 1.33 kg net. The sprocket body is made from steel or sintered iron, forming the KSR25-L0 design. The compact sprocket-and-bearing arrangement allows direct mounting into the chain line without a separate support bearing, simplifying installation where a fixed idler position is required. As a unitized component, it keeps the sprocket and rolling elements aligned as a single assembly, reducing setup effort compared to separately mounted sprockets and bearings. Selection should be based on the bore size of 25.0 mm and outside diameter of 52.0 mm matching the surrounding chain and mounting geometry.