The underwriter's over-allotment allocation in a securities offering, a standard feature of a public offering. This gives an underwriter the right (but not the obligation) to purchase additional stock in connection with a public offering. The green shoe is typically an additional 15 percent of the agreed-upon underwriting amount. The theoretical purpose of the over-allotment allocation is to permit the underwriter to stabilize the after-market for the companies' securities during the period immediately following a public offering. The over-allotment allocation is universally exercisable by the underwriter at any time during the 30 days following the IPO, including at the IPO closing. By purchasing additional securities available pursuant to the green shoe and immediately reselling the stock to the public, thereby increasing the public float, the underwriter can maintain a balance between the demand for a company's stock and the supply of stock available to satisfy the demand.