My father was making custom ethernet cables and wondered why he only got 100mbps despite the cable being cat6, after redoing the connectors, 1gbps came up. : r/techsupportgore
Metz CAT 7 MC GC1000 Plus23 Ethernet Cable Custom
RJ45 to BT431A or CAT5 to BT431A Cable "Custom Made Lengths" Free 1st Class Post | eBay
bit-tech Looks at CableMod's Custom Cables | bit-tech.net