Dapol O Gauge 7A-000-011 3 Link Instanter Wagon Coupling & Drawbar Hook Pack of 5 Pairs

Five pairs of assembled metal 3-link couplings with central T shaped Instanter link.
This version of the simple 3-link coupling allowed the coupling length to be quickly shortened when a train was formed, bringing the wagon buffers close together, reducing the slack in the train without the expense in cost and time of fitting and adjusting screw couplings. First introduced by the GWR in the 1920s for use on vacuum braked express goods trains most British Railways vacuum brake fitted wagons were equipped with these couplings.