Four independently movable blades aligned in two parallel pairs oriented rectangular to each other. The setup allows to define the size of the aperture opening independently in width and height with a side length from 0 to 20 mm. Position sensors allow for closed-loop positioning of each blade to precisely define the size and the position of the aperture within the 20 by 20 mm window of the enclosure. Specialized versions are available for the use in high and ultra-high vacuum environments. Customized versions are also available. Please do not hesitate to contact us to discuss your specific requirements.