The Great Lakes CM-13 is Single Cable Ring, 1.06"W x 2.80"D
Question: How does this attach to the APC Rack?
Answer: Thank you for your inquiry,
The Great Lakes CM-12s mount between rack holes on the vertical mounting rails of any standard rack. Esentially the cutouts on the unit would fasten under screws attached the rail. You can also use misc screw holes within your rack to mount them.