These are a good product and price. Only issue i found was that you need to be VERY careful when tightening these down. Especially if you are tightening them into graphite or reinforced-plastic. Apply a bit of moly grease to get them to go in smoothly. If you force them too much it is liable you will snap the ball off of the screw. Otherwise they are a good 4/5 product.
I buy to replace in my HPI sprint 2. The HPI BALL CUP 4.3x15.5mm (z125) was brocked and itīs very hard to find. Also, it's necessary replace the original HPI ball cup with 3RAC-BE4816. These 2 parts together are cheaper than the z125 HPI BALL CUP.