The bit operates like a communication channel between rider and horse. As the mouth is one of the most sensitive parts of the horse’s body it is important to treat it very carefully. Therefore a bit should be sized and fitted to the individual anatomic shape of the mouth as well as to the characteristic needs of the horse and should never be uncomfortable or awkward in any way. There are two factors to consider when choosing the size of a bit: - Width - Thickness Width Bits with loose rings With correct attaching of bit with loose rings, there should not be more than 0.5 cm space on the right and left between mouth corner and bit ring. The ring should always be freely movable and should not pinch the mouth corner.   Bits with fixed cheeks e. g. eggbutt, Full cheek or D-Ring bits Bits with fixed cheekpieces such as eggbut or D-ring bits should fit closely to both mouth corners and must therefore be Chosen smaller than loose ring snaffles. Due to the contact of the cheek to the corner of the mouth the rider achieves additional support from the rein aids. Double bridle The double bridle consists of a weymouth and a bradoon. The bradoon should equal the standard snaffle in size and shape because it lies at the same position in the horse’s mouth. The weymouth is positioned a Little bit lower where the horses head gets thinner. We recommend to choose the weymouth 0,5 to 1 cm smaller than the bradoon in order to achieve the best possible effect and to make it most comfortable for the horse.     Thickness The thickness of a bit should be adapted to the anatomic needs of your horse. A study of Sprenger and the Veterinary University of Hanover found that the oral cavity of horses is fairly small and the available space for a bit can be very limited. You cannot draw conclusions from the body size of your horse to its oral cavity.     To find out what thickness you should choose for your horse you can try the “2-finger-test”. You just need to put your index and middle finger together and insert them in the horse’s mouth at the point where the bit usually lies. A small gap between the upper and lower jawbone will exert pressure on both fingers and will require a thinner mouthpiece (14 – 16 mm) in order to fit comfortably. If you feel only little or no pressure on your fingers there is space for a thicker mouthpiece (16 - 18 mm).   Using a too thick bit will exert pressure on the sensitive palate and will cause bruises and injuries. The horse might react with head tossing, gaping its mouth or jerking on the reins.