Slightly wider is all.
SCC is always updating to new sizes.
LEB Hobbies and Carrera Slots also carry them.
One thing to try and remember is that one size of these tires can fit many wheels with a little stretching.
Example:
The 22125 tire shown above fits the 17 wheel but also fits the smaller 15 size wheels. It just stretches over and just need to true a little.
Once you start working with his tires, you will get to know what fits what pretty fast.