Siemens 3SE5212-0BK21 Enclosure width 31 mm acc. to EN 50047. Siemens 3SE5212-0BK21 is the exact printed commercial reference for a limit or safety switch in the SIRIUS 3SE range. Siemens' official product description is: Position switch Metal enclosure according to EN 50047, 31 mm Device connection 1 x (M20 x 1.5) 1 NO/1 NC slow-action contacts Twist lever, 21 mm long right/left adjustable with plastic roller 19 mm.