20m Cat 5 Network Cable

Twenty metres is a between-floors length: down a stairwell, along a landing and into a bedroom, or the full depth of a flat from the entrance to the back room.

At this distance a cable stops being a convenience and starts being the reason the connection works at all, because it is well past where a Wi-Fi signal has to fight through two walls. Moulded RJ45 plugs at both ends. A hundred in stock at five dollars.