Aki™ rollers are covered here by one part, a 39mm adjustable sliding door carriage with an acetal roller in a plastic body, which also replaces Stegbar® rollers. On doors of this type the wheel fails rather than the housing: acetal wears flat where the panel sits when it is not used, grit from the track grinds into it, and the door starts to judder or needs lifting to move at all. The adjustment screw is what lets the panel be levelled again once the new carriage is fitted. Because this one part spans two brands, match it on size rather than on the name on the door. Remove the old carriage from the bottom rail and measure the body length, as 39mm is the identifying dimension and neighbouring sizes look near identical until they are side by side.