Can someone explain me the PCI-E slot variations & sizes

Handle 0x001D, DMI type 9, 17 bytes System Slot Information Designation: J6B1 Type: x1 PCI Express Current Usage: In Use Length: Short ID: 1 ==

On a motherboard with PCI Express slots, each PCI Express slot is connected length on a motherboard At higher clock rates, data transmitted

pcie4 slot The size of an module is marked by its form factor The form factor defines the width by length in millimeters For example, the form factor 2260

pcie 4 nvme in pcie 3 slot Expansion card riser specifications ; Slot 1, Riser 1, Low Profile, Half length, x16 ; Slot 3, Riser 2c, Low Profile, Half length, x16