Triple Square Bit
A 12-pointed star-shaped fastener tool commonly used on European vehicles for high-torque applications.
A triple square bit, also known as an XZN bit, is a specialized 12-pointed star fastener tool. It is created by overlaying three squares at 30-degree angles. Triple square fasteners are widely used on European vehicles (such as Volkswagen, Audi, Porsche, and BMW) for high-torque applications, including cylinder head bolts, driveshafts, brake caliper carriers, and steering components.
The 12-point design distributes torque over a wider surface area than standard hex or Torx fasteners, allowing for extremely high tightening torque without the tool slipping or stripping the bolt head. However, because they look similar to Torx or double hex fasteners, DIY mechanics often attempt to use the wrong tool, which instantly strips the inner teeth of the triple square fastener, making it extremely difficult to remove.
If a triple square fastener is stripped, removing it requires specialized bolt extractors or welding a nut to the bolt head. Mechanics inspect these fasteners for debris before inserting the bit, ensuring it is fully tapped into the bottom of the screw head. Having a complete set of XZN sockets is essential for anyone performing suspension, engine, or transmission work on European cars.