When you want a super skinny Ethernet / CAT-6 cable, this noodle-y UTP jumper is only 3mm thick at the center so that it can flex around enclosures easily. This cable is 30cm long, about one imperial foot, comes in Adafruit black. CAT6 means it's great for Ethernet-based LANs and other data networks. UTP means the wires are unshielded - much thinner but not great for ultra-long lengths (that's why it's only 30 cm)
This is a 'straight-thru' cable, not a cross-over cable. If you need an Ethernet cross-over cable, this one won't work.