Provides guided return of a roller chain by combining a sprocket with a bearing unit mounted on a fixed bore of 15.0 mm, with an outside diameter of 40.0 mm and a net mass of 0.2 kg. The sprocket is made from steel or sintered iron, forming a compact idler unit designed to run directly on the chain without additional support elements. The fixed bore diameter allows direct mounting on a shaft or axle without adjustment for radial play, making the unit suited for chain guiding or tensioning positions where the running track must stay fixed. The compact outside diameter and low mass keep the unit lightweight for installation in confined chain runs, while the combination of sprocket and bearing in one unit simplifies alignment between the chain and its support point.