The Myler Flat Shank with Sweet Iron Low Ported Barrel Narrow (MB 43LP, Level 2-3), made from sweet iron with copper mouth inlay, offers significant relief for your horse's tongue. The mouthpiece has a 1 1/4" port and does not rotate on the tongue like some other bits.
Details
\n
The Basics: Sweet iron with copper inlay. Sweet iron will oxidize naturally over time, is harmless to horses, and its sweet taste encourages salivation.
Level Up: Myler's unique "level" system means there's a bit for your horse no matter their training. Level 2-3 bit offer precise control through ported mouthpieces that relieve your horse's tongue, however there will still be some degree of pressure for correction. Ideal for moderately experienced horses or horses who show resistance to Level 1 and Level 2 bits. 
\nBenefits of a Flat Shank: Flat shanks are curb bits that require less contact than other bits. They are well-suited for advanced, dexterous riders who use soft hands with horses who respond well to light bit pressure. 
\nIndependent Side Movement: Entire shank moves independently from the mouthpiece which means more control and clearer communication between you and your horse.