Inno Sense Curbgag Mullen BitTrust Inno Sense Curbgag Mullen Bit Bits with a flexible mouthpiece can be used on all horses, however, they are especially suited to young horses or horses with a sensitive mouth. The plastic is FDA approved, which means the material in non toxic and contains no plasticisers. Additionally, the bits are very sturdy due to the use of a flexible core made of stainless steel. Available in Hard or Soft Thickness: 20 mm Sizes: 12. 5 cm 13. 5 cm 14. 5 cm