The two get mixed up all the time. A straight bar is exactly that, dead straight, and it lies flat across the tongue. A mullen has a soft arch, which leaves the tongue a little more room and spreads the pressure across the tongue and the bars instead of concentrating it.
Neither has a joint, so there’s no nutcracker action and nothing to poke into the roof of the mouth. If you’ve been searching for what a straight bar bit does, it does much the same job as a mullen with slightly more tongue pressure. The Happy Mouth Loose Ring Straight Bar is the best-known example.
The mouthpiece is one solid piece, so both reins act on the whole of it. That makes the contact very simple and very steady. It also means a rein aid on one side moves the whole bit, so the signal is less independent than it is with a jointed snaffle. You’ll notice it in lateral work, and it’s worth knowing before you ask for a tight turn.
A mullen can do two quite different jobs. For a horse that’s busy and light in the mouth, it encourages him to push his tongue forward into the contact. For one that’s happy in a contact, it curves around the tongue and presses evenly when the reins are used together.
The horse who objects to the movement of a joint is the clearest case, and busy, fussy mouths often settle once the bit stops moving about. Plenty of youngsters start in a soft mullen for the same reason.
The exception is a horse with a thick, fleshy tongue and a low palate, who may find a full mullen too much tongue pressure. A ported mullen keeps the stability but gives the tongue room. The Myler Hanging Cheek MB06 Low Port Mullen Barrel is a good example. Thickness matters just as much, and our guide to what thickness of bit your horse needs will help.
Metal gives the most precise feel and lasts longest. The Shires Blue Sweet Iron Loose Ring Mullen is an inexpensive way to find out whether your horse likes one, and the AB Eggbutt Mullen Mouth is the more refined choice.
Nylon and plastic are lighter and warmer, and many have a little flex, such as the Flexi Bits Mullen Mouth Loose Ring and the Eggbutt Nylon Mullen Mouth. For the softest feel of all, rubber and vulcanite mullens are usually found on Pelhams, such as the Soft Flexible Rubber Mullen Pelham.
Softer materials do get chewed, so look them over after every ride. Our guide to checking your horse’s mouth after riding explains what to look for on the horse, too.
Mullens come on most cheeks, including the Pelham and hanging cheek.
The metal mullens, including the AB Eggbutt, can be taken on a 30-day Bit Bank trial. Nylon and rubber bits are purchase only, because they can’t be sterilised to the standard the library needs. Happily, they’re also the cheaper ones. If you’d like advice on whether a mullen is right for your horse, call our Bitting Specialists on 01405 861800, option 3.