The NDUV503A is a Neutral Density Filter from Thorlabs, designed with a circular shape and a diameter of 0.5 inches. It features a UVFS reflective coating on both the front and back, offering an Optical Density (OD) of 0.3. This filter is designed for use with SM05-threaded mounts, making it compatible with a wide range of optical systems. The geometry of the filter includes a thickness of 1 millimeter, contributing to its overall compact design. The NDUV503A is currently in stock and available for purchase through the Thorlabs website.