These binding posts are made from gold plated brass and can either take wire or 4 mm banana plugs. All binding post come in pairs. Both, K42Au (left) and the same looking K11/45/Au (not pictured), have screws for tightening the wire. The others, K30Au (centre) and K10Au (right) come with clamping nut. If binding posts are mounted on wood insulating sleeves are not required.