A crop header arranged for cutting and transporting a standing crop comprising: a draper assembly arranged such that cut crop falls onto the draper assembly for transportation relative to the header; the draper assembly including a draper guide roller and a continuous loop of belt material wrapped defining an upper run of the belt material on top of the roller and a lower run of the belt material below the roller, wherein the belt material includes a generally horizontal upper edge portion of the upper run of the belt material; a generally horizontal top support wall of the header adjacent to and spaced from the edge portion of the belt material; and a sealing member attached to the top support wall for spanning and sealing between the upper edge portion and the top support wall; and wherein the sealing member comprises a strip of a flexible material which extends from a first portion of the strip overlying the top support wall to a second portion of the strip which lies over and in contact with the upper edge portion of the upper run, and a bracket extending between a front edge and an opposite rear edge; characterised in that the rear edge of the bracket terminates over the support wall so that the bracket includes no rearward extending portion beyond the top support wall which biases the strip toward the upper run, and the rear edge acts to pinch the first portion of the strip onto the top surface of the top support wall; and wherein the strip, when free from loading forces, contains a distortion from a flat form so that a plane of the second portion is distorted from a plane of the first portion in a direction toward the upper edge portion of the upper run forming an angle between the plane of the second portion and the plane of the first portion. a draper assembly arranged such that cut crop falls onto the draper assembly for transportation relative to the header; the draper assembly including a draper guide roller and a continuous loop of belt material wrapped defining an upper run of the belt material on top of the roller and a lower run of the belt material below the roller, wherein the belt material includes a generally horizontal upper edge portion of the upper run of the belt material; a generally horizontal top support wall of the header adjacent to and spaced from the edge portion of the belt material; and a sealing member attached to the top support wall for spanning and sealing between the upper edge portion and the top support wall; and wherein the sealing member comprises a strip of a flexible material which extends from a first portion of the strip overlying the top support wall to a second portion of the strip which lies over and in contact with the upper edge portion of the upper run, and a bracket extending between a front edge and an opposite rear edge; characterised in that the rear edge of the bracket terminates over the support wall so that the bracket includes no rearward extending portion beyond the top support wall which biases the strip toward the upper run, and the rear edge acts to pinch the first portion of the strip onto the top surface of the top support wall; and wherein the strip, when free from loading forces, contains a distortion from a flat form so that a plane of the second portion is distorted from a plane of the first portion in a direction toward the upper edge portion of the upper run forming an angle between the plane of the second portion and the plane of the first portion.