msi slotB key slot for ‘B’Key card (also known as Socket 2) (SATA) M key slot in ‘M’Key card (also known as Socket 3) (PCIe x 4) B+M Key cassettes are available for both cassette slots. Check HDD and SSD support specifications.MSI B760M Bomber WiFi Motherboard, Micro-ATX - Supports 14th13th12th Gen Intel Core Processors, LGA 1700