but they do add a bit of much needed size/weight to the tiny Joy-Cons,

Joy Cons do a great job sliding in and Out.

The wheels hold the Joy-Cons snugly and securely, and make controlling the drifting (SR button) and item throwing (SL Button) feature of the game much easier to use.

So much better than using the Joy-Cons alone for Mario Kart.

The wheels are small, much like the Joy-Cons, and are about 5" in diameter (or about the size of a DVD).

Works great with the Switch Joy-Cons, especially for Mario Kart.

These do work well and added a little "meat" to the Joy-Cons that are, by themselves, almost to small for my hands.

They work just fine with our Joy-Cons.