Two carriages here suit Horizon™ timber sliding doors, both 83.1mm, one with an acetal roller and one with a metal roller. That pairing is the useful part of the page: on a timber slider it is the wheel that goes rather than the carriage body, flattening where the door rests and picking up grit from the track until the door has to be shoved instead of slid. Choosing between the two comes down to the track and the leaf — acetal runs quieter and is easier on a worn track, while the metal roller suits heavier doors and harder use. Before ordering, take the door off and measure the carriage body end to end, because 83.1mm is the identifying dimension and timber door carriages of similar shape are made in several lengths. Check the mounting hole spacing against the old part as well.