Both types are used with the CM491 series vandal resistant lobby panel modules and mini alphabetical directories.
The 19" height on the OF291 (flush) is ideal for mounting alongside standard 19" high vertical mail boxes, if required. The OF291S (surface) frames are open in the back to allow for equipment clearance and wiring as well, but can surface mount right on the wall without the need for a surface back box or housing. The OF291 (flush) frame can be used by itself, or with the matching OH191 flush back box/housing.
NOTE: All models are 19.00"H (483mm). Surface models are 2.25"D (58mm). Flush models are .88"D (23mm) off of finished wall surface
The OF291S (surface) frame shall be open in the back to allow for equipment clearance and wiring if needed.
Contractor shall observe all local and national electrical codes, and contractor shall provide a model S1 special screwdriver for future system maintenance.