A runner rating is not the rating of the whole vanity
Premium drawer systems publish load classes for particular runners, lengths and installation conditions. Those figures are useful, but they describe the compatible hardware configuration rather than every custom drawer that happens to use a similar runner.
The completed load also depends on the drawer box, fixings, cabinet material, cabinet width, wall support and how the drawer is used.
Bathroom drawers carry unusual loads
A vanity drawer may hold bottles, grooming tools, spare products, towels and cleaning materials. Users may also lean against the open drawer while reaching for something. A wide drawer full of heavy bottles is a different engineering problem from a narrow drawer holding cosmetics.
The exact runner specification should therefore be recorded with the cabinet design. Do not use a catalogue figure as permission to overload an unverified custom box.
Ask for the system, not just “soft close”
Soft-close describes motion. It does not identify the runner, load class or cabinet construction. A proper specification should record the hardware manufacturer, system, length, load class and compatible drawer dimensions.
That information makes future adjustment and replacement much easier.
Read why drawer runners should have real part numbers, or see the vanity serviceability guide.