What is PCIe? Understanding PCIe Slots, Cards and Lanes

According to the spec sheet for a Molex PCIe connector, the rise from the mounting surface to the top of the socket is

A PCIe x16 slot has a physical length of approximately 89mm and has a single notch on the connector PCIe x16 devices are not compatible with smaller PCIe slots

pcie x 16 slot PCI-E and PCI-X Card Guidelines ; 1UXXL PCI-X Full height, half length · 133 MHz ; 1UEEL PCI-E Full height, half

pcie 40 gpu in 30 slot PCIe x1: These are the smallest PCIe slots, used for almost any other cards like average network adapters and USB expansion cards · PCIe x4: