How do I choose a bit with the right thickness?

Traditionally people have believed that a fat mouthpiece is kind and a thin one is severe. But this isn't a universal rule - many factors need careful consideration including the horse’s anatomy, breed, age, level of training, bit size and rider competence. Another critical factor is the conformation of the horse's mouth. If there is insufficient room in the horse’s mouth then fat is not kind.  A bit that's too fat for the limited space within the mouth may even impair the horse’s ability to breathe and swallow especially when coupled with hyper-flexion (behind the vertical).  

While we have established that a large weight bearing surface is going to be milder in relation to the forces we put on the tongue through the reins, we need to consider the other effects that a thick bit might have on the mouth. If the bit is too thick, the horse may struggle to close their mouth around the bit comfortably, without causing damage to the unforgiving upper palate.

If the bit is causing pressure between the sensitive bars of the mouth, or on the upper palate the horse is likely to open their mouth to avoid the discomfort, and what happens then? We strap the mouth shut with a flash noseband! So the pressure has increased further and it’s now unavoidable.

In cases like this, where the horse perhaps has a particularly small mouth combined with a large tongue, it may be milder to use a slimmer mouthpiece.

The ideal however would be to keep the benefit of a large weight-bearing surface that the thicker bit offers but with less bulk between the bars and against the upper palate (A Neue Schule Turtle Tactio is ideal in this situation).

Thinner mouthpieces (10mm, 12mm, 14mm)

The 10mm thick mouthpieces have been designed to fit pony mouths perfectly.

12mm – 14mm thicknesses are useful for horses which have thicker tongues and lips.  The thinner mouthpieces deliver a more intense pressure (your rein aid is delivered over a smaller surface area of the tongue and lips and is therefore slightly stronger, think of a stiletto in contrast to a regular heel); we find this is ideal for cob types which are a little less responsive to the rein aid than you ideally want.

Thinner mouthpieces are also useful if you have a horse with little room in the mouth as the thinner mouthpieces take up less room in the mouth.  For example the horse below is quite fleshy in the lip so a thinner mouthpiece will result in a more intense pressure and a more responsive ride.

Intermediate mouthpieces (16mm)

If you are confused by all the jargon and are comfortable that your horse is fairly average in terms of oral anatomy a 16mm will offer a good weight bearing surface and is well accommodated by most horses.

For younger horses we tend to recommend a 16mm+ thickness mouthpiece to help them become comfortable with taking the bit.  Thinner mouthpieces can occasionally result in young horses backing off the bit as the pressure can be a little too sharp when establishing basic acceptance of the rein aids.

Thicker mouthpieces (18mm, 21mm)

We find mouthpieces of this nature can be too thick and can actually impede the horse’s way of going as they can prevent horses from closing their mouths properly.

We tend to recommend 18mm and 21mm thick mouthpieces for horses that back off the contact and are very sensitive in the mouth as they are milder in action.  If you opt for a thicker mouthpiece, we recommend checking that your horse has adequate room to accommodate the bit in his mouth.

Competition regulations:  If you are competing FEI Dressage or Eventing Dressage, your snaffle bit must be no thinner than 14mm in diameter for horse and young horse classes and no thinner than 10mm for pony dressage*.

*While we do everything possible to ensure the information provided is accurate, the responsibility lies with the competitor to stay up to date with rule changes and ensure they are using approved/permitted equipment.