Seven replacement parts on this page suit BGC® windows, sliding and patio doors, and framed shower screens. Three are sliding door carriage and roller assemblies — a 15kg medium duty adjustable unit that replaces the Mk2 roller, and two adjustable nylon carriages with acetal rollers that also suit Jason™ doors. The rest are a keyed window vent lock and the shower screen hardware: pick-up blocks in black and white, and a set of three sill blocks. That mix shows where these systems give out — rollers flatten and jam under panel weight, vent lock barrels seize, and the plastic blocks that carry and locate a shower panel crack at the sill. Pull the old carriage out and measure its body length and wheel diameter before ordering; on shower blocks, match the colour and the profile to the existing set.