Abstract: An improved expansion assembly for an expander tool is provided. The expander tool is used to expand a surrounding tubular body within a wellbore. Accordingly, a method for expanding a surrounding tubular is also provided. The expansion assembly first comprises a piston disposed within a recess of the expander tool. The top surface of the piston closely receives a pad. The pad is held in close proximity to the top surface of the piston such that it does not rotate about a shaft. This arrangement reduces the geometric size of the expansion assembly, affording a larger inner diameter for the hollow bore of the expander tool itself. At least one reinforcement member is disposed on or within the pad to strengthen the pad during an expansion operation. The reinforcement member is fabricated from a durable material, and is arranged along the pad in the area of contact with the surrounding tubular during an expansion operation.