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The Innovators in Trailer Design

"Duo-fit" Coupling Fitting Instructions

This trailer coupling has been designed to fit the two different diameters of tow balls commonly used in New Zealand. These being 1 7/8” and 50mm diameters.

  1. Identify the diameter of the tow ball the coupling is to be fitted to. This diameter is normally stamped on the flat on top of the ball. If the size is not shown the ball will need to be measured. Diameters will be either 1 7/8” or 50mm.
  2. Observe the safety lock protrusions on each side of the coupling stem beneath the handle. These protrusions are marked 1 7/8” on the right side and 50mm on the left side.
  3. Lift the coupling handle up as far as it will go and rotate it left or right until the safety trigger lines up with the protrusion marking that matches the ball diameters. Note the handle cannot be rotated unless fully up.
  4. With the handle in the up position, place the coupling over the tow ball and release the handle. It will automatically lock into place as will the safety trigger.
  5. When manufactured, the coupling has been adjusted to suit new tow balls. If fitted to a worn tow ball, any looseness can be removed by adjustment of the screw fitted to the nose of the coupling. Loosen the lock nut and adjust the screw until it touches the tow ball. This adjustment should be made on level ground and with weight taken off the coupling. Tighten the lock nut when complete.
  6. For long life, the inside surfaces of the coupling head and the lock pin should have a smear of grease applied at regular intervals.