The tow-ball mount required two pairs of pivots. To operate satisfactorily, it also needed tubing sleeves running through each pair of bearings to allow support from simple 10mm bolts. The mount is universal and the pivots are used in a variety of ways: from folding steps to folding bike-racks and folding luggage carriers. The environment on a car tow-ball is aggressive due to salt spray and road dirt, so the sleeves were liable to corrode in the cast bearing housings. Standard steel tubing is only easily available in 12.7mm diameter. The casting has 12.2mm pivot bores. Cost is important for FMCG.
Pete Yates realised a plastic iglidur® sleeve bearing available in standard metric sizes (12mm OD, 10mm ID) would have enough compressive axial strength to allow clamping with a through bolt and washers. It would also allow a standard bolt to pass through and provide the corrosion resistance required.