Indoor/Outdoor Backbox for NBG-12 Series; except NBG-12LRA, use in outdoor applications with NBG-12LO “Only”. UL listed.

Back box: Surface-Mount: For Use With PS-SA And PS-DA Models
SB-I/O surface-mount backboxes are for use with Silent Knight® PS-SA and PS-DA pull stations. In addition to being molded out of increased UV stabilized polycarbonate material (94V-O), these backboxes have mounting holes and bottom conduit entries that"

SB-IO Surface Mount Back Box Data Sheet