A new type of image dissector tube is described. The tube contains new electro-optics involving a combination of ring-electrodes and a metallic mesh. The positioning of the mesh is determined by a relation involving the number of focusing loops. The LRM tube (from loop-related-mesh positioning) implies that very high resolution can be obtained at fairly low accelerating voltages. The resolution is uniform over the whole photocathode when dynamic focusing is used. The high resolution is obtainable in tubes where the ratio between the photocathode diameter and the length of the image section is as high as 0·4. Thus large photocathodes can be combined with short tube lengths. An LRM tube design with a 100 mm photocathode diameter and an image section 250 mm long is described.