In a linkage device for flap rudders for watercraft, in particular ships, a first bearing housing includes a sliding piston and a first sliding bearing, and a second bearing housing includes a linkage pin and optionally a second sliding bearing. The first and the second bearing housings and/or the sliding piston and the linkage pin and/or optionally the first and the second bearings each have substantially the same diameter and/or substantially the same width and height.