Will a visor from another brand fit my helmet?

Almost never. The mechanism differs between brands, between ranges inside a brand, and sometimes between two generations of a model that kept its name. A visor fits the models its maker lists, and that list is the whole specification.

Why there is no standard here

Nothing obliges makers to share a visor fitting, and each has designed its own — the pivot, the ratchet, the seal and the release are part of how the helmet was approved as a whole object. A visor from elsewhere is outside that, which is a separate matter from whether it can be clipped on.

What to match

The visor part number the maker lists for your exact model, in its exact generation. Where a helmet has been through a revision, the maker publishes which visor goes with which — and a helmet bought second-hand may already be carrying a replacement visor from a different generation.

The trap in the photograph

Curved pieces of tinted plastic look identical in a listing. Two visors from the same brand, for two helmets in the same range, can differ in the position of one lug. A listing without a compatibility list is a listing to leave alone, whatever the picture shows.

The second thing the part number decides

Whether the visor carries the pins for an anti-fog insert. Prepared and unprepared versions of the same visor exist side by side and photograph identically, and the pins cannot be added later — so a visor bought without them is a visor that can never be made to work properly in winter.

The one case where another brand’s visor fits

Some open-face helmets take a generic three-snap visor, which genuinely is interchangeable and costs very little. That is a fitting convention rather than a standard, and it applies to that one style of helmet.