Product review (5 stars): Great Product but Be Careful!
This is a great product and well worth the money. There are several YouTube videos showing you how to install them. Be warned, it's not simply a snap on here and snap there, as I found out with my first wheel!

The wheels/rollers and the studs/axles do not come with instructions or diagrams. In fact, the video showed that you snap on the stud first, then attach the roller to the stud. INCORRECT. If you do it in that order, you will have considerable difficulty snapping on the roller. Luckily, I figured it out and was able to remove the stud/axle carefully without breaking it.
The correct way is to place the roller on a flat, hard surface and snap the roller on to the stud first. Then it's a breeze snapping the combo on to the legs of the rack.
Also, apparently there are THREE different types of studs available. The ones that come in this package seem to be sturdier and better than the original "rotational" type part my machine came with.
I replaced all 8 rollers and original studs and the rack slides effortlessly back and forth, no bent rollers or broken studs. While the rollers usually last quite a while, the weak point seems to be the studs. If your original studs are the rotational type that rotate to snap on, those are liable o fail eventually. The much better design are the direct, snap on ones that come with this package. Zoom in on the photos provided to see the detail.
Very pleased with the final result and highly recommended. Hope the install review helps others. Took about 20 minutes to fix, including my initial whoopsie!