A magnetic mat for holding surgical instruments. The mat includes a plurality of magnet holders configured to removably receive magnets therein. The magnet holders are connected together using a plurality of links so as to form a two dimensional mat adjustable in size. As a result, the effective magnetic surface area of the mat may be extended to provide adequate coverage for larger patients and thereby prevent instruments from falling off the patients' surface. In embodiments, the magnet holders may be opened such that different magnets may be inserted, removed, replaced and/or exchanged. Additionally, the magnet holders, links, and/or magnets may be independently sterilized, and/or replaced. In embodiments, the magnet holders include an open cage structure to hold a magnet with minimal obstruction of its magnetic field.