A filter element comprises a pleated metal fiber fleece being pleated according to pleating lines providing an edge with pleat openings to be closed in order to make gas flowing through the metal fiber fleece. The adapter assembly includes two adapters that have collars to hold a night vision monocular between them, and to each connect with a camera and lens, respectively, modifying a camera-lens assembly for use in night time photo surveillance. The knitted loops of the front collar knitting portion are transferred to a needle bed wherein knitted loops of the back are retained, the knitted loops of the one neckline are returned to an original needle bed, and a front collar knitting portion is knit on the one neckline. , alkali and alkaline earth metal hydrides.