On the 4x4, the maximum size material that can be carved is infinite feet long, 4ft wide, and 4 inches thick.
On the 4x2, the maximum size material that can be carved is infinite feet long, 2ft wide, and 4 inches thick.
When cutting through material thicker than 2", the bit must be able to cut through this thickness without the collet nut hitting the sides of the material. Advanced toolpath may be required.