Genuine correct NOS 4mm speaker sockets, for HARBETH, QUAD & others, Quad 606 / 909, 99 & others.
Accepts 4mm plugs. Threaded part approx 4.5mm, big hole for bigs wire approx 4.5mm also accepts 4mm plug in side.
DO NOT CONFUSE THESE WITH MANY CHEAP VERY INFERIORS TYPES.