B-Line Eaton series open racks, 11 Gauge steel, Plates, and #12-24 mounting hardware, Mounting spaces: 1, 1/2" Space between racks, Yellow zinc, 23"

It's an adapter that lets you mount standard 19 inch rack panels in a 23 inch equipment rack. The part is a 23 inch equipment rack to 19 inch panel mount adapter plate, sold as a set of two plates with #12-24 mounting hardware. Telco-style 23 inch frames are common in central office and older comm rooms, so this is what you use when the gear you bought is 19 inch EIA width.

No. #12-24 mounting hardware is included with the pair of plates. #12-24 is the thread used on most B-Line open frame racks, so the screws match the frame you're mounting into. Whatever hardware your 19 inch panel itself requires still comes with that panel.

One mounting space. The plates are specified at 1 mounting space with 1/2 inch of space between racks, so you lose a single RU position where the adapter sits. Plan your panel layout around that one space.

One order covers one panel position. The part ships as two plates, one for each side of the rack, plus the #12-24 hardware. If you're adapting multiple 19 inch panels in a 23 inch frame, order one per mounting space you need.

If the 23 inch frame is already installed and anchored, adapter plates are the cheaper path and keep the existing frame in place. If you're building a new room and all your gear is 19 inch EIA, put in a 19 inch rack and skip the adapters, since each one consumes a mounting space and adds a step at every panel. Adapters make sense for retrofits and mixed-width equipment in legacy telco frames.

Order Eaton B-Line model SB576A01YZ. The YZ suffix is the yellow zinc chromate finish.

11 gauge steel with a yellow zinc chromate finish. Yellow zinc gives indoor corrosion protection, which is fine for a comm room or equipment closet but not a plated finish intended for outdoor or wash-down exposure.