A crop harvesting header with a cutter bar and a draper assembly has a draper driven by a drive roller at one end and an idler roller at the other end. The draper is carried on a plurality of support rollers parallel to the first and second rollers for supporting the upper run of the draper at spaced positions therealong. The draper 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 an integral extruded sealing member extending along the cutter bar defining a first stiffer portion attached to the cutter bar and a second flexible blade portion 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.