BST is an older generation of Boral® hardware rather than a current range, and five parts here cover it: an 8mm multi-link plastic sliding door carriage and acetal roller in a two pack, keyed and non-keyed window catches with springs, and a black flyscreen retaining spring clip sold singly or in a ten pack. On hardware of that age the failures are predictable. The catch spring goes soft so the sash no longer holds, the plastic carriage links crack, and the flyscreen clips lose their temper and drop the mesh frame out of the reveal. The same clip also replaces Old Comalco™ clips, which helps if the window carries no marking at all. Measure the carriage across the 8mm roller before ordering, and check whether the catch you are replacing is keyed or non-keyed.