Sweet iron will rust when it comes into contact with (air) humidity; the surface rust tastes sweet and naturally stimulates the saliva production. This will cause the horse to salivate more which in turn encourages better acceptance of the bit. The rusting process (oxidation) changes the blue colour of the TRUST-bit to a brownish-grey.
If a sweet iron bit is not used for a while, an orange-brown rust layer may develop on the mouthpiece. Simply remove this by wiping the bit with a damp cloth.
The Beval bit is an ordinary bit with extra eyes on the inside of the bit rings. This bit has a similar effect as a Pessoa bit and 3-ring bit but it works softer and has less leverage effect. The upper eye is used to attached the bit to the bridle. The bottom eye is for the reins.