Most popular today are the Kadee and knuckle. Kadees are preferred by scale and some hirail operators because they appear more prototypical. Kadee makes an S scale #802 and an HO #5 (both suitable for S scale). Knuckle couplers are popular on AF trains and most hirail products. Early AF also came with link couplers but were abandoned in the early 50s for the knuckle couplers.

The knuckle-shaped devices at the ends of locomotives and cars. The “horn-hook” style was developed several decades ago by the National Model Railroad Association to encourage mass-produced HO scale equipment. The “Rapido-style” coupler is the de facto standard for N scale. In recent years, however, more manufacturers have been offering their stock equipment with more-prototypical looking “knuckle”-style couplers, such as those first made popular by Kadee.

Controls in the console which connect together the various keyboards, so that while playing upon one, the stops drawn upon another also sound (INTER-couplers, e.g. Swell to Great); or transferring the played keys upward or downward an octave on the same keyboard to increase the range or shift the register of the stops drawn (INTRA-couplers, e.g. Swell to Swell 4'). Couplers permit the greatest possible number of combinations of stops and, in effect, extend the reach of the organist's hands and feet.

A grooved insert and ring for the decorating bags that allows tip changes without changing bags. The coupler has two parts; the inner coupler base and the outer coupler ring.