Bridles may be made of leather, webbing or synthetic material, and are secured by stitching, buckles and billets. They are available in three main sizes (pony, cob and full) and are fully adjustable. The standard cavesson nose band can be changed to a different style if required.
To check the fit of a bridle:
The headpiece, which forms the main part of the bridle (in combination with the cheek pieces), should lie comfortably behind the horse’s poll
The brow band should rest across the horse’s forehead (preventing the headpiece from slipping backwards), with a clearance of two finger widths to prevent the headpiece from pinching the ears
It should be possible to place two fingers under the cavesson noseband if this is correctly fastened
The cheek pieces should be buckled equally and should allow the bit to lie comfortably in the mouth, creating only a slight wrinkle at the corner of the lips
The bit should lie flat in the horse’s mouth, with approximately one centimetre of clearance on either side of the mouth
Taken From Blue Cross