Square D (Schneider Electric) NSYMM86 Electrical Box Hardware And Accessory. Schneider Electric Square D™ Mounting Plate For Use With: Special™ S57 Fixed Cover Box Special™ S3D CRN S3X and Thalassa™ PLM 800 mm H x 600 mm W Enclosure Specifications: 135 kg Permanent Permissible Load M8 Screw 2.5 mm THK Galvanized Steel Plain 750 mm H x 550 mm W x 125 mm D Dimensions. Additional Description: SQD -NSYMM86 Metal plain chassis 800X600. Catalog Description: Schneider ElectricMetal plain chassis 800X600Plain galvanizedSpacial S57galvanised steelmounting accessorymounting plateset of 1.