WSM-1820-25 is an e-chain flexible polymer bushing manufactured by Igus. It is designed to provide a quiet and reliable actuating system with minimal friction. It has an outer diameter of 20mm, inner diameter of 18mm, and a length of 25mm. It is made of a low friction plastic material, and comes in a yellow colour. This part has a sleeve bearing, which means that it has a sleeve that slides along the inner diameter of the bearing, allowing it to rotate and creating a platform with minimal friction. It is designed to be used in a wide range of applications, including v-belts, chains, and cams.