Pcie 3 16x extension cables

hello
new here just looking for info and parts to make my own pcie gen 3 16x extension cable for custom pc build

Greetings,

PCIe connectors are designed as a card edge interconnect system, meaning that half of the connector set is formed by a copper pattern on the PCB of the device using the connector. Accordingly, there isn’t much available in the form of (for example) a crimp-on connector that implements that half of the connector set; if you really want to make your own, you’ll probably end up making custom PCBs to do it. That won’t be as straightforward as one might expect, since maintaining controlled impedances is needful due to the high speeds on the PCIe bus.

My sincere recommendation, unless you’re planning to start a business selling pallet loads of the things, would be to buy one of the numerous commercially-produced cable assemblies for this purpose.