What is the plastic clip on a car seat belt called UK?

The plastic clip on a car seat belt is called a seat belt buckle or seat belt clip. In UK vehicles from brands like Vauxhall, Jaguar or MINI, this component is part of the seat belt's fixed mechanism that includes the tongue, anchor points and retractor. Seat belts (called safety harnesses in some UK documentation) are mandatory safety devices that restrain occupants during collisions, preventing secondary impacts with the steering wheel, dashboard or ejection from the vehicle. Modern UK-spec cars typically use high-strength polyester webbing for the belt material with metal or reinforced plastic buckles that meet ECE R16 safety standards.