The Icelandic bits are unique in the equestrian world. The mouthpiece is attached to the shanks in such a way as to allow movement in all directions.
The special feature of the Icelandic bit is the loose chain. The chain is not fastened more than needed to make the shank angle at 90° - 100° from the mouth and it is often looser. The chain on the Icelandic bit is set so that it touches the horse only slightly or not at all when the horse is vertical flexed at the poll. If the horse moves its head upwards and against the rein the chain immediately takes effect and the horse feels an increased pressure, which in turn guides the horse to seek the position where there is no pressure and it is comfortable.
A well-educated horse will become even better when ridden with an Icelandic bit, but a badly trained horse can become even worse.
The Icelandic Long Shank is best suited to the experienced rider with soft hands.