The Sweet Iron Low Ported Barrel is a great mouthpiece for the horse that does not respond well to tongue pressure.

7" Cheeks, 5 1/4" Mouth. Stage C.
The width of Reinsman's ported barrel provides plenty of room for the horse's tongue to pass underneath, and when engaged does not rotate onto the tongue.
This bit works primarily off of bar and lip pressure with some poll and curb involvement.
The sweet iron naturally rusts into a light patina which tastes sweet, increasing salivation for a supple mouth.
The 7" S Cheeks have a fair amount of leverage and combined with the Low Ported Barrel make it easy to isolate each side of the horse's mouth for lift, bend and flex.

760 Reinsman Seven S Sweet Iron Low Ported Barrel Curb Bit - 5 1/4 Inch