Wastegates and wastegate components

A wastegate assembly is disclosed comprising: a plug (1040) configured to plug a wastegate opening wherein the plug comprises a concave, at least partially spherical surface (1046); a shaft (1070) configured for receipt by a bore in a wastegate chamber; and a rotatable arm (1055) extending from the shaft wherein the arm comprises a convex, at least partially spherical surface (1052) configured for contacting the concave, at least partially spherical surface (1046) of the plug for a closed orientation of the plug with respect to the wastegate opening.