The Ground Industries Terraintula wheels are aluminum with carbon fiber.
The Crosshair hubs are plastic.
They fit mountainboard trucks so 12mm axle, but you can probably switch out the bearings if you want.
Here is the description on the terraintulas:
"These are brand new Ground Industries 200 x 50 Balistik Mountainboard tires and Black Terraintula aluminum and carbon fiber hubs. They are not in the original packaging, but come in a mesh bag that can be used for storing pads. Set includes 4 tires, 4 tubes, and 4 hubs. They also include 8 brand new 12mm bearings. These hub and tire sets will fit most mountain board trucks. Original retail for this set was well over $300 so this is a super value for an awesome product! Feel free to contact me if you have any questions."