The UMP45 is a compact submachine gun with a sleek, angular design, featuring a polymer frame and metal components. It has a distinctive short barrel, collapsible stock, and a top-mounted rail for optics. The weapon's surfaces are a mix of matte black finishes and slightly worn metallic parts, showing signs of frequent use. The grip and stock are textured for better handling, and the magazine is prominently visible, adding to its utilitarian aesthetic.