Replacement roller assemblies are what TradeBase carries to suit Alspec® heavy aluminium sliding doors — three of them, all high load. Two are 90kg tandem assemblies at 90mm, one of which also covers Capral™, Ullrich®, G.James® and Vantage™ assemblies; the third is a 150kg quad roller assembly at 150mm with the same cross-brand fitment. Nothing else appears here, and that is the point: on doors this size it is the roller assembly that fails, not the frame. Bearings pick up grit and grind, wheels flatten under the weight of a large glazed panel, and the door starts to drag or lift in the track. The millimetre figure in each title is the identifying dimension — the length of the assembly body — so measure the old assembly once it is out and count the wheels, because a tandem and a quad are not interchangeable.