a header frame;

an elongate cutter bar arranged along a front edge of the frame;

a knife mounted on the cutter bar for cutting the standing crop;

a draper assembly mounted on the header frame rearwardly of the cutter bar such that out crop falls onto the draper assembly for transportation longitudinally of the header;

the draper assembly including a first and a second draper guide roller each arranged at a respective end of the draper assembly spaced apart along the cutter bar with an axis of each guide roller arranged substantially at right angles to the cutter bar;

the draper assembly including a draper canvas forming a continuous loop of flexible material wrapped around the rollers so as to define an upper run of the draper canvas on top of the rollers and a lower run of the draper canvas below the rollers and so as to define an outer surface of the draper canvas which faces outwardly of the loop that the outer surface forms the upper surface of the upper run and the lower surface of the lower run and an opposed inner surface of the draper canvas which faces inwardly of the loop;

a front edge of the upper run of the draper canvas being arranged underneath the cutter bar, and a rear edge of the upper run of the draper canvas being spaced rearwardly of the cutter bar;

a front draper support plate defining a substantially horizontal support surface lying under the upper run adjacent the front edge thereof and extending therealong between the first and second guide rollers;

the first and second guide rollers each having a front end thereof recessed rearwardly of the front edge of the upper run of the draper canvas and the support plate having a front edge thereof recessed rearwardly of the front edge of the upper run of the draper canvas such that the upper run of the draper canvas includes a portion thereof at the front edge which is cantilevered forwardly of the rollers and of the support plate;

the draper canvas including a base layer of a sheet material having a front edge of the base layer defining the front edge of the draper canvas and a rear edge of the base layer defining a rear edge of the draper canvas;

the draper canvas including an additional strip of a resilient material attached on to the outer surface of the base layer at or adjacent the front edge of the base layer so as to stand outwardly from the outer surface of the base layer and extending rearwardly from the front edge of the base layer to a rear edge of the additional strip spaced rearwardly of the front edge of the base layer and forwardly of the rear edge of the base layer;

the additional strip standing outwardly of the outer surface from the base layer to define an outer surface of the additional strip raised from the base layer;

the cutter bar including an element thereof extending rearwardly over the upper run of the draper canvas to a position rearwardly of the front edge of the upper run of the draper canvas and forwardly of the front end of the rollers and of the front edge of the support plate and engaging the outer surface of said additional strip on the draper canvas so that the engagement between the element of the cutter bar and the outer surface of the additional strip forms a seal to inhibit entry between the cutter bar and the draper canvas of materials carried by the cut crop.