The Australian manufacturer issue a set of dish style idler wheels to customize the AFV Club model and resin tires to replace the vinyl ones that come with the kit.

The dish style idler wheels

The idlers come in a zip-lock bag. They are cast in a light beige resin easy to work. The cast is perfect with only some flash inside the holes. The detail is excellent, noticeably on the wheel hub and the inner faces of the wheels.
The assembly of both halves is perfect thanks to a positioning notch. The idler arm axle fits straight into the idler inner face. Nonetheless, the hole of the inner face is not drilled throughout the wheel so the axle can't totally enter its location. We'll need to either cut the axle or drill out the idler half wheel.
Half of the parts being in contact with the pouring lugs, the wheel tread will need a thorough sanding.

The road wheels tires

They are designed to replace the vinyl ones that come with the AFV Club kit and avoid the unpleasant surprises due to the contact between painted plastic and vinyl tires.
The zip-lock bag contains 26 tires. They are cast in a light grey resin and present a good level of detail. If the parts closely look like the vinyl parts they are less thick by 0.5mm and their tread is angled which will require a little sanding.
About 10 tires are larger than the roadwheels generating a gap (up to 0.5mm) which will create troubles when centering the parts. This will require to sand the excess of resin to have all the wheels sitting properly at the same height.
Some tires have tiny air bubbles some of which are inside the tires and will be hard to fill.

Conclusion

The idlers sets is highly recommended to those who want to customize their Centurion or simply model a specific version.
The replacement tires will be better used by modelers who dislike vinyl parts. Their real advantage over the kit vinyl parts is they enable to depict worn out wheels.