These Calypso Wheels from Ethic DTC are 30mm wide with a 125mm diameter which is the biggest on the market. The larger wheel and bearings will destroy all terrains, roll faster and last longer. You'll need 12mm axles to ride these big boys.
 
Price is per wheel
 
Wheels Diameter - 125mm
30mm wide urethane
Weight - 0.72 lbs (328g)
12 STD Compatible - Yes
Hardness - 88A
Bearings Included - Yes