what is the opening width of this?

The opening width of this rack is 19.8 inches externally and 17.7 inches internally.

Questions & Answers: StarTech RK12WALLOA Wall Mount Server Rack - 12U Rack - 12 - 20 in Adjustable Depth - Open Frame - Network Rack - Computer Rack - Equipment Rack

double click image to zoom in

StarTech RK12WALLOA Wall Mount Server Rack - 12U Rack - 12 - 20 in Adjustable Depth - Open Frame - Network Rack - Computer Rack - Equipment Rack

Mount your server or networking equipment to the wall, using this adjustable 12U open frame rack
Easy installation with mounting points positioned 12 and 16 in. apart to match standard wall studs
Flat-packed for easy and cost-effective shipping
Network rack / server rack / Computer rack / Equipment rack / open frame rack / 12U server rack / 12U wall-mount rack / wall mounted rack / small server rack / 12U rack