Fits BA20D / Bosch BA20D bayonet bulbs. Designed forBosch‑style BA20D bayonet bulbs. Designed for BA20D Bosch‑Type Bulbs. This bulb holder is engineered for use withBA20D bayonet bulbs, commonly referred to asBosch BA20D bulbs, which were widely used across older motorcycles, scooters, and modern Chinese machines.