Since I don't have the specific product details (e.g., is it a mechanical keyboard switch, a K-Pop song, or a tech gadget?), I have drafted a review based on the most popular result: the (likely the "Boba" style linear switch often associated with the number 91 or similar nomenclature in the enthusiast community).
The most specific reference to "91switch" is found in the custom mechanical keyboard community. 91switch