The cheeks of these bits extend both upward and downward, tapering as they get farther away from the mouthpiece, with a half-moon ring similar in shape to the Dee-ring or eggbutt (depending on the design). The long sides provide a great deal of lateral guiding effect. The full cheek without bit keepers is more fixed in the mouth than a loose ring, and thus has a similar action to the eggbutt or Dee-ring. Use of bit keepers, however, makes the full cheek even more fixed than the Dee-ring, concentrating bit pressure on the bars and tongue.
Sweet Iron - will rust when in contact with humidity (air). The surface rust tastes sweet and naturally simulates the salvation production. This will cause the hors to salivate more which will encourage the horse to take more contact.
The process of rusting (oxidisation) changes the blue colour of the Trust bit to a brownish - grey. A sweet iron bit will develop an orange-brow rust layer on the mouthpiece if it is temporarily not used. This is easily removed by wiping it off with a damp cloth.