SK51201 is in 3.5" FDD form factory compatible for two hot-swap 2.5" SATA HDDs. It is mechanically well designed with great EMI performance and also equipped with HDD failure and activity
SK51101 is in slim FDD form factor, compatible for one hot-swap 2.5" SATA HDD. It is mechanically well designed with great EMI performance and also equipped with hard drive failure and access
SK51102 is in slim ODD form factor, compatible for one hot-swap 2.5" SATA HDD/SSD. It is mechanically well designed with great EMI performance and also equipped with hard drive failure