Carriages and rollers for sliding aluminium windows, sized by overall carriage length. Adjustable and fixed types in acetal, nylon, brass and stainless steel. Measure the old carriage end to end and match the length — the wheel profile and axle material are listed on every product. Window carriages are lighter duty than patio door carriages, so check the load rating before substituting one for the other.
Not sure which one? See the Sliding Door Roller & Carriage Buying Guide, look up a part number in the roller part number finder, or browse all rollers and carriages.