Professional’s Choice Bit - Short Double Bar Chain PCB-913All cheeks pieces are stainless steel. All mouthpieces are sweet iron. These bits will rust when exposed to moisture. This creates a sweet taste in the horses mouth and promotes salivation. Mouth: 5. 5 Cheek: 7 Provides the same great feel as the 8 shank with a softer, lighter leverage effect. Chain: The chain mouthpiece is mild yet more aggressive than a two or three piece snaffle mouthpiece.