Four replacement carriage and roller assemblies are listed as suiting Rylock® sliding doors and windows. Two are 25kg patio door carriages, one front-adjustable and one rear-adjustable. The other two are a 13mm adjustable plastic carriage with an acetal roller in a 2 pack, which also replaces Lidco® rollers, and a 38.6 x 15.7mm stainless adjustable carriage and roller. Rollers are the whole range for this brand, and that is the honest picture — the wheel and its bearing give out long before the aluminium does, and the door starts dragging on the sill. Take the old carriage out before ordering. Check whether the adjusting screw sits at the front or the rear of the door, then measure: 13mm and 38.6 x 15.7mm are the dimensions that separate these assemblies from one another.