A harvesting header (40) operable to harvest a crop. The header has a flexible cutterbar assembly (48) extending lengthwise in a lateral direction relative to the normal direction of travel of the header. The cutterbar assembly is supported from a plurality of laterally spaced apart support arms (44,46) which are pivoted about a laterally extending axis so that the cutterbar assembly can flex along the length thereof in response to changes in terrain as the header is advanced. A pair of stops cooperate to define a variable range of angular movement of the support arms and a corresponding variable range of generally vertical movement of the flexible cutterbar assembly. A first one of the stops is configured to engage at least one of the support arms and thereby define a first upper limit of the range of angular movement, and second one of the stops is adjustably spaced from the first stop and configured to engage the at least one support arm and thereby define an adjustable second lower limit of the range of angular movement. The second can be selectively positioned in an arm-locking position, in which the at least one support arm is concurrently engaged by both stops and the cutterbar assembly is thereby generally restricted from moving vertically, and a plurality of spaced apart arm-swinging positions defining corresponding distinct ranges of angular movement for the support arms.Linvention porte sur un organe de coupe (40) utilisable pour la récolte de cultures. Lorgane de coupe comporte un ensemble barre de coupe (48) souple sétendant longitudinalement dans une direction latérale par rapport à la direction normale de déplacement de lorgane de coupe. Lensemble barre de coupe est supporté par une pluralité de bras de support (44, 46) latéralement espacés et amenés à pivoter autour dun axe sétendant latéralement de telle sorte que lensemble barre de coupe peut sinfléchir sur sa longueur en réponse à des changements du terrain pendant l’avancée de lorgane de coupe. D
