BOTH ROUND & SQUARE HOLES: One side round holes beams are for sound equipment mounting with 10-32 screws, while the other side square holes beams are for rack shelves and 19” network equipment mounting with M5 & M6 screws STURDY TOP& BOTTOM PLATES: Half cabinet half rack designing. 6U 4 post open frame rack with reinforced top & bottom vented plates, a good balance between air ventilation and firm structure, is convenient to put your laptop, laser projector, game console, CD player, or even a beautiful plant on the rack. This open frame 6u rack supports maximum 500 lbs.（220 kg）of rack mounting equipment with leveling feet, and 400 lbs. (180 kg) equipment with casters UPGRADED SUITE: RIVECO enthusiast 6u network rack suite meets your one-stop-shop needs. Including all necessary hardware: assembly screws & cage nuts, leveling feet and casters and one piece of 8 outlets PDU for daily usage VARIOUS SIZES: 19.7 " (500 mm)(W), 21.7" (550 mm)(D), 17.4"（442 mm with casters）(H). There are more sizes 9U, 12U, 15U, 18U ,22U,25U to choose from SIMPLE INSTALLATION: Easy assembly according to instruction with all hardware within a few minutes. If you do need move the rack from time to time, you can install casters and for heavier equipment, you will need to install leveling feet for securing home server rack to the floor RIVECO 6u server rack with one piece of rack shelf & PDU. We consider this series as of half cabinet & half rack, with top & bottom panels, but open frames sides. OFCO racks are widely used for electronics & equipment like AV, TV, NAS, DATA, server, internet router, amplifier, hard recorder, computer, X-box.