Instanter couplings are similar to the standard 3-link coupling, except that the middle link has a complex shape with two 'ears' allowing it to be placed in either of two positions, corresponding to 'long' or 'short'. In the 'long' position, the coupling has the ease-of-use of the 3-link. In the 'short' position, some of the 'slack' is taken out of the coupling and the motion of the train less "jerky".