Top Lock Narrow or Slim (TL19) – Top Lock Narrow or Slim measures 19mm wide on outside and 16mm on inside. There are two variations of the arm as some vehicles, the arm is offset slightly and on other vehicle is straight without the offset as shown in the image. This is standard width for .most arms of this style found on Alfa Romeo, Aston Martin, Audi, Volkswagen, and Porsche. The quickest way to determine if your top lock arm measures 19mm or 16mm on inside, is to use a penny. A penny will fit snugly into the end of the wide 19mm wiper arm. It will not fit into the end of the narrow 16mm arm