Monoprice is known for their quality merchandise.  Each box comes with 2 of the 6 ft long ducts with covers - for a total of 12 ft.  Easy to cut to size as needed.  Versatile for use with networking cables or anywhere you have several power cords/cables to utilize - with the open slots not only providing circulation but also ease of having different cords come out at different places along the way as shown.  Highly rated.  Great for anywhere from the garage to the office.  MSRP $33 per box.  Save over half.
 
Monoprice Open Slot Wiring Raceway Duct with Cover: This 2-pack features 1.0"x1.8" ducts, each 6 feet long in gray, designed for easy re-routing of terminated wires and added cable support with its 8mm wide fingers. It's compatible with 22 AWG networking cables and comes with pre-drilled mounting holes. Dimensions are 200.66 x 5.72 x 3.81 inches, and it weighs .3 ounces.