Bits with a flexible mouthpiece can be used for all horses but are especially suitable for young horses and horses with sensitive mouths. The plastic is FDA approved, which means that the material is non-toxic and contains no plasticisers. In addition, the bits are very sturdy due to the use of a flexible core made of stainless steel. Whilst the Medium density mouthpiece has some flexibility it has a distinctive level of rigidity suited to sensitive but forward going horses.