Are PCIe brackets standardized?

Gembird PCI Express Slot Replacement Bracket PC Tower Desktop pcie slot bracket PCI Rear Slot Cover for all circular power connectors This PCI bracket allows easy connection for the AC adapter in legacy systems Just insert this PCI pcie 1 slot Search for pci slot bracket Get fast shipping and top-rated customer service RIITOP NVMe PCIe Adapter NVMe to PCIe x4 Converter Card

pcie 50 slot Shuliwen PCI Slot Cover 12pcs PCI Slot Cover PCI L Blank Bracket PCI Expansion Blank Plate Supply Nvme Pcie Ngff Ssd To Pcie X1 Adapter Card Pcie X1 To M