A serrated panel for a wind turbine blade, wherein the panel is configured to be attached to the trailing edge of a blade to form a plurality of serrations at the trailing edge of the blade, wherein the serrated panel comprises: - a base part for attaching the panel to the trailing edge of the blade, the base part having - a first longitudinal end for arrangement nearest a tip end of the wind turbine blade, - a second longitudinal end for arrangement nearest a root end of the wind turbine blade, - a first side for arrangement nearest a leading edge of the blade, - a second side for arrangement farthest from the leading edge of the blade, - an attachment surface for attaching to an exterior surface of the wind turbine blade, and - an exterior surface facing away from the exterior surface of the wind turbine blade, when the serrated panel is attached to the wind turbine blade, and - a plurality of serrations extending from the second side of the base part, wherein the serrations comprise a base proximal to second side of the base part, and an apex distal to the second side of the base part with a notional line extending from a midpoint of the base to the apex, characterised in that the serrated panel contains exactly two discrete alignment protrusions (91, 92) that protrude from an attachment side of the serrated panel, the two discrete alignment protrusions (91, 92) being configured to abut a trailing edge of the wind turbine blade and thereby align the serrated panel relative to the trailing edge of the blade. - a base part for attaching the panel to the trailing edge of the blade, the base part having - a first longitudinal end for arrangement nearest a tip end of the wind turbine blade, - a second longitudinal end for arrangement nearest a root end of the wind turbine blade, - a first side for arrangement nearest a leading edge of the blade, - a second side for arrangement farthest from the leading edge of the blade, - an attachment surface for attaching to an exterior surface of the wind turbine blade, and - an exterior surface facing away from the exterior surface of the wind turbine blade, when the serrated panel is attached to the wind turbine blade, and - a first longitudinal end for arrangement nearest a tip end of the wind turbine blade, - a second longitudinal end for arrangement nearest a root end of the wind turbine blade, - a first side for arrangement nearest a leading edge of the blade, - a second side for arrangement farthest from the leading edge of the blade, - an attachment surface for attaching to an exterior surface of the wind turbine blade, and - an exterior surface facing away from the exterior surface of the wind turbine blade, when the serrated panel is attached to the wind turbine blade, and - a plurality of serrations extending from the second side of the base part, wherein the serrations comprise a base proximal to second side of the base part, and an apex distal to the second side of the base part with a notional line extending from a midpoint of the base to the apex, characterised in that the serrated panel contains exactly two discrete alignment protrusions (91, 92) that protrude from an attachment side of the serrated panel, the two discrete alignment protrusions (91, 92) being configured to abut a trailing edge of the wind turbine blade and thereby align the serrated panel relative to the trailing edge of the blade.