PCIe test solutions

Can someone explain me the PCI-E slot variations & sizes pcie slot sizes PCI-E X16 Slots can run in x1, x4 , x8 and x16 modes so you can install a x1 card in a x16 slot without worries of shorting anything as long as pcie 50 x16 slot 1 slot = 20mm, with the width of 110mm

pcie slot size Card capacity and size · Slot 1: gen 4, up to x16 lanes · Slot 2: gen 4, up to x16 lanes · Slot 3: gen 4, up to x8 lanes