One of my MOT failure points is the top ball joint gaiters. I bought the sng clear replacements (with the extra fitting rings)
I didn't really know how they would fit so looked on this forum to see what others had done. It seems that people have had problems fitting the ring that the gaiter then slides over. It certainly did not fit easily, but can be prised on with a 1/2" piece of metal (or possibly a teaspoon). Also the ring has a top and bottom, I believe that the top that locates on the metal wishbone recess is the more pronounced lip.
Then its a case of fitting the gaiter itself which is reasonably easy if fitted from the back first then squeeze the fat part progressively to pop it on. For belt and braces I will add lock wire.
Hope the above makes sense and might be of help to someone. Sorry if it's been covered elsewhere.
Steve.