The Dee Ring is very similar in action to the Eggbutt, it will prevent pinching of the lips and gives a slightly more solid feel against the side of the face. It also prevents the bit being pulled through the mouth. The release is slower and some slight poll pressure is introduced.
The Barrie is a severe bit due to the center links of the two pieces being offset by 20 mm giving it a double nutcracker action, which creates more tongue and bar pressure.
The Round Twist creates more pressure points on the bars making it a stronger bit.
Good for strong older horses.