On 17 November 2016, JL Cheatham in Virginia, USA wrote:
"I restored a pair of Rainbow wiper arms. See bottom of page here). -- I had replaced my wheel boxes with new ones from Moss and found that the splines of the new spindles did not match the splines of the Rainbow arms. I ended up restoring my original wheel boxes with new rubber seals from Todd Clarke. The Rainbow splines fit perfectly on the original spindles".

On 18 November 2016, JL Cheatham wrote:
"Here's a picture of the new Moss spindle I bought compared to the original spindle. There are fewer splines on the new Moss Spindle (57) compared to the original spindle (72). Original Rainbow wiper arms will not fit on the Moss spindles".

So, if you want to buy the Moss Motors wiper spindles, you also need to buy the Moss Motors wiper arms and install them as a matched set. For future service, this precludes use of original type parts unless you once again buy both spindles and wiper arms and change them as a matched set. As always when using any non-standard parts you should keep good documentation, and keep in mind that the non-standard parts may not be available later for future service. Replacing the spindles (wheelboxes) is royal pain in a fully assembled car, especially if all you wanted to do was to replace the wiper arms.