Abstract: A compact three-bar linkage steering probe assembly, particularly useful with ultra-narrow row cotton harvester units, includes two vertical rocker arms pivotally connected to a harvester row unit at mid-point locations and upper ends connected by a cross link to generally constrain the arms for rocking in unison. Crop guides connected to the lower ends of the rocker arms follow the bases of the plant stalks as the row of plants enter the unit. The vertical arms are maintained within spacer tubes which prevent interference with adjacent rows of plants and which assure the arms are not disturbed by the adjacent rows. A sensor responsive to rotation of the rocker arms is located at the central pivotal connection. Arm leaf springs or a spring biased adjustable upper cross link provides probe flexibility for accommodating different plant stalk sizes.