Bit Bank Australia can highly recommend you purchase a copy of the Myler's new and revised Book and DVD set, The Level Best for Your Horse if you are at all interested in the Myler bits. Even if you are not using a Myler Bit, the book has much information to offer on general bitting and the way we interact with the horse's mouth. You can order the book and DVD set onlinehere.
An excerpt from The Level Best for Your Horse
Our belief that tongue relief is the key to achieving a relaxed horse has not changed. If anything, we believe in it more strongly today than we did ten years ago. We've worked with equine dentists and chiropractors to explore the relationship between the muscles of the mouth, jaw, neck, shoulders, back and hindquarters; advances have been made that support our belief that interfering with the horse's ability to swallow impedes overall balance and motion. Tongue relief remains the underlying principle of the Myler Bitting System (...)
(...) Remember that the Myler System is a graduated system and the end goal is to find the mouthpiece that makes your horse as comfortable and relaxed as possible by giving hims as much tongue relief as he can handle without sacrificing your control and communication (...)
(...) Finding the mouthpiece most suitable for your horse is only half of the puzzle. The other half is finding the cheekpiece that helps you communicate most efficiently and clearly through that mouthpiece (...) The mouthpiece is for the horse, the cheekpiece is for the rider.
To order your FREE 17 page brochure on An Introduction to the Myler Bitting System, click here.
EA/FEI Dressage and Competition Permitted Myler Bits
It is true that currently, a lot of the Myler bits are not legal for Dressage or Pony Club. Bits that are FEI dressage and PC legal are marked as so in the shop listings. However, as you spend 90% of your time training and only 10% of your time competing, there is no reason why you should not still consider a Level 2 or 3 bit, even if it not be permitted in competition.
See below for a pictorial listing of the approved/ not approved Myler bits, courtesy of Zilco.