Features:

• Rockville RAIL18U 18U Reversible Rack Rails With M5 Circle or Square Screw Holes
  
• Dimensions: 2.28” x 1.02” x 33.9” (inches)
  
• Replace or upgrade the rack rails in any standard 6U Rack
  
• Use the circle M5 holes if you prefer to just screw your gear right into the rack quickly
  
• Use the square holes if you want to protect your gear and install with screw and cage nuts’