A crop harvesting header with a cutter bar and a draper assembly has a draper which includes a front edge of the upper run of the draper arranged at a position adjacent to but spaced from the cutter bar and there is provided a sealing member extending along the cutter bar. The sealing member is co-extruded to form a constant cross-sectional shape along the full length and to define a first portion of a stiffer plastics material attached to the cutter bar and a second blade portion of a more flexible plastics material which extends rearwardly from the first portion at the cutter bar to lie over and in contact with a bead along a front edge portion of the draper.