Abstract: A replaceable tool for attachment to the periphery of an agricultural disc is formed of an inverted U-shaped investment casting which can be fitted over the marginal edge portion of the disc to present parallel leading and trailing faces connecting side surfaces which converge outwardly of the disc, being inclined at different angles relative to the plane of the disc so as to present on one side of said disc a side surface providing clearance for the disc on that side of the disc and the other side surface being at a greater angle which reduces the areas of the end faces of the tool to reduce resistance to passage of the tool through the ground.