They have a lot of runout on the wheels. You can just dress it out if you're using AO wheels, or shim it out.
I turned the wheel mounting plate, and that improved the runout, but I really need to true-up the shaft and the spuds for the wheel plates, like some of the folks here have done.
In other words, it's a kit, but they work pretty well, especially considering that they're usually on sale for $99.
"Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."