My coach is not an Axis but when I bought it I had the dealer install extenders as a condition of sale.
The ones installed are I believe Dicor stainless steel braided extenders.
One point to note is that if you have a TPMS installed or are planning to install one the extenders should be supported so the weight of the TPMS cap/valve does not cause the extender to loosen due to tire rotation.
Here is a pic of the system installed on my coach. Although I have polished aluminum wheels Dicor also makes a set that secures to wheel liners.
The bracket that secures the extender is secured to the hub cover.