(c) References to a bit in western performance classes mean the use of a curb bit that has a solid or broken mouthpiece, has shanks and acts with leverage. All curb bits must be free of mechanical device and should be considered a standard western bit. A description of a legal, standard western bit includes: (1) 8 1/2” (215 mm) maximum length shank to be measured as indicated in the diagram. Shanks may be fixed or loose.
(2) Concerning mouthpieces, bars must be round, oval or egg shaped, smooth and unwrapped metal of 5/16” to 3/4” (8 mm to 20 mm) in diameter, measured 1” (25 mm) from the cheek. However, wire on the sway bars (above the bars and attaching to the spade) of a traditional spade bit is acceptable. They may be inlaid, but must be smooth or latex wrapped. Nothing may protrude below the mouthpiece (bar), such as extensions or prongs, including upward prongs on solid mouthpieces. The mouthpiece may be two or three pieces. A three-piece, connecting ring of 1 1/4” (32 mm) or less in diameter, or a connecting flat bar of 3/8” to 3/4” (10mm to 20 mm) measured top to bottom with a maximum length of 2” (50 mm), which lies flat in the horse’s mouth, is acceptable.
(3) The port must be no higher than 3 1/2” (90 mm) maximum, with rollers and covers acceptable. Broken mouthpieces, half-breeds and spades are standard.
(4) Slip or gag bits, and donut and flat polo mouthpieces are not acceptable.
(5) A curb bit must be used with a curb strap or curb chain properly attached so as to make contact with horse’s chin.