Hot swap up to four 3.5 SATA or SAS hard drives using three 5.25 bays - 4 Bay 3.5" SATA SAS Backplane - Hot Swap Mobile Rack for three 5.25" Bays - Trayless design - Supports SAS I/II and SATA I/II/III - 4 bay mobile rack with durable plastic and aluminum construction provides a cost-effective solution for drive maintenance and hot swapping drives between systems - 2 fans and venting to optimize heat dissipation - HDD Rack - SAS Backplane - SATA Backplane - 4-bay SAS/SATA backplane