Choosing the right bit for your horse comes down to three things: fit, function, and listening to your horse. A bit that fits correctly, suits your horse's anatomy and level of training, and is made of quality material will result in a relaxed, responsive horse with a light, consistent contact. A bit that doesn't fit — or doesn't suit — will show up as resistance, tension, or soreness, often mistaken for a training problem. This guide walks you through the key decisions, step by step.
How Do I Know If My Horse's Bit Fits Correctly?
The most common bitting mistake isn't choosing the wrong mouthpiece — it's using a bit that doesn't fit correctly in the first place. Two dimensions matter most: width and thickness.
Bit width is measured as the inside dimension of the bit. For loose ring snaffles, there should be no more than 3–5mm of space between the bit ring and the corner of the mouth on each side. Bits with fixed side pieces — olive heads, D-rings — should sit close to the corner of the mouth, and are typically sized half a centimeter smaller than a loose ring snaffle.
A bit that is too wide will slide around, create uneven pressure, and may cause soreness at the corners of the mouth. A bit that is too narrow will pinch.
Bit thickness should match the space available in your horse's mouth — and that space is often smaller than riders assume.
Research commissioned by Herm Sprenger and carried out by the University of Veterinary Medicine Hanover found that horses' mouths are flatter and more limited in space than previously thought.
A quick way to check: place your index and middle fingers together in the space where the bit sits. If you feel pressure on both fingers when the horse closes its jaw, a bit of 14–16mm thickness is appropriate. If there is more room, 16–18mm may work. A bit that is too thick can press on the palate — causing pressure points, head tossing, and resistance that riders sometimes misread as a training problem.
Single Jointed or Double Jointed — What's the Difference?
Once you have the fit right, think about mouthpiece action.
Single jointed bits act primarily on the edges of the tongue and the lower jaw. When the reins are tightened, the joint rises slightly in the center, directing pressure toward the tongue's edges.
Conventional single jointed bits have shanks of slightly uneven length due to manufacturing, which means pressure is not perfectly symmetrical — it's worth turning the bit regularly, or choosing a model like the Herm Sprenger Turnado or Dynamic RS, in which the joint is angled 45° forward to ensure even contact on both sides.
Double jointed bits distribute pressure over a larger area of the tongue, including the center, without the joint pressing into the palate. This makes them a gentler starting point for many horses, particularly those that are sensitive or just beginning their training. The KK Ultra from Herm Sprenger is the best-known example — its 45°-angled centerpiece ensures no palatal pressure and has made it one of the most widely used training bits in the world.
Neither type is universally "softer" or "stronger" — it depends on the horse's anatomy, the rider's hand, and the training situation.
Loose Ring or Fixed Side Piece — Which Is Right for My Horse?
The side piece determines how quietly the bit sits in the mouth and how directly rein aids are transmitted.
Loose ring snaffles allow some movement between the ring and the mouthpiece, which can absorb slight inconsistencies in the rider's hand. The horse can also momentarily lift the bit with the tongue to briefly relieve pressure.
This makes them a good choice for young horses and less experienced riders.
Fixed side pieces — olive heads, D-rings, full cheek snaffles — attach the mouthpiece firmly to the ring, so the bit lies more quietly and rein aids are transmitted more directly. They also provide additional lateral contact, which can help with horses that tend to drift or break out through the shoulder.
The trade-off is that an unsteady hand is transmitted directly to the mouth without the cushioning effect of a movable ring.
Does Bit Material Really Matter?
Most quality bits are made of stainless steel or copper alloys. Stainless steel is neutral — tasteless, odorless, and durable — but does not encourage the horse to salivate or chew.
Copper alloys oxidize naturally, creating a slightly sweet taste that stimulates saliva flow and chewing activity. This is desirable: a horse that chews and salivates freely is a relaxed, supple horse. However, not all copper alloys are created equal. Conventional copper alloys use aluminum as a hardener, which actually inhibits the oxidation process and defeats the purpose. Herm Sprenger's proprietary Sensogan alloy uses manganese instead, which preserves the natural oxidation and therefore maintains the salivation-stimulating effect. It has been toxicologically tested and assessed as safe by the University of Veterinary Medicine Hanover.
One practical note: the natural oxidation of Sensogan and Aurigan bits causes the metal to darken over time. This is not a defect — it's the process working as intended. Discoloration can be easily removed with Herm Sprenger's Diamond Bit Paste, which is formulated specifically for this purpose and safe for regular use.
What Is My Horse Telling Me About the Bit?
A horse going well in a correctly fitted bit will typically show: a relaxed topline, quiet and regular chewing, a light and consistent contact, and an appropriate, willing response to rein aids.
Signs that something may be wrong with the bit include: head tossing or shaking, opening the mouth, consistently leaning on the hand or going behind the contact, excessive chewing or bit-playing, resistance when bridling, and redness or soreness at the corners of the mouth or on the tongue. These behaviors are not always a training issue — before assuming a rideability problem, check the bit.
Note that health issues — dental problems in particular — can produce identical symptoms. A dental check should always precede a bit change if issues arise suddenly.
When Should I Ask for Professional Help?
Bit selection is a skill that develops over time. If you are unsure where to start, try borrowing before buying — some retailers offer bit trial programs. Consult your trainer, an equine dentist, or a qualified bit fitter. And when in doubt, a well-fitted, correctly sized loose ring snaffle in a quality material is almost always a safe starting point.
At HorseHaus, we carry a curated selection of Herm Sprenger bits across mouthpiece types, side piece styles, and sizes. If you have questions about which bit might suit your horse, reach out — we're happy to help.
Quick Reference: Bit Fitting at a Glance
Loose ring snaffle: 3–5mm space between bit ring and corner of mouth on each side
Fixed side pieces (olive head, D-ring): sit close to the corner of the mouth, typically ½cm smaller than loose ring
Bit thickness: use the 2-finger test — pressure on both fingers means 14–16mm; no pressure means 16–18mm is fine
Happy horse signs: relaxed topline, quiet chewing, light and consistent contact
Unhappy horse signs: head tossing, open mouth, leaning, soreness at corners of mouth
When in doubt: start with a loose ring snaffle in 16mm Sensogan
Frequently Asked Questions
How do I know if my horse's bit is the right width?
For a loose ring snaffle, there should be no more than 3–5mm of space between the bit ring and the corner of the mouth on each side. Fixed side pieces such as olive heads and D-rings should sit close to — but not pinching — the corner of the mouth.
What is the 2-finger test for bit thickness?
Place your index and middle fingers together in the space in your horse's mouth where the bit sits. If you feel pressure on both fingers when the horse closes its jaw, choose a bit of 14–16mm thickness. If there is more room and little pressure, 16–18mm is appropriate.
What is the difference between a single jointed and double jointed bit?
Single jointed bits direct pressure primarily to the edges of the tongue. Double jointed bits distribute pressure over a larger area of the tongue, including the center, and are generally considered more even in their action for many horses.
What is Sensogan and why does it matter?
Sensogan is Herm Sprenger's proprietary copper alloy, hardened with manganese rather than aluminum. Unlike conventional copper alloys, it preserves the natural oxidation process that stimulates the horse's saliva flow and chewing activity. It has been independently tested and approved as safe by the University of Veterinary Medicine Hanover.
Why is my Herm Sprenger bit turning dark?
Darkening is caused by the natural oxidation of the copper alloy — this is intentional and desirable, as it is what encourages your horse to chew and salivate. It can be removed with Herm Sprenger Diamond Bit Paste without affecting the bit's function.
Is a thicker bit always softer?
Not necessarily. A bit that is too thick for the space available in your horse's mouth will press on the palate and cause discomfort. Thickness must match the available space — the 2-finger test is the most reliable way to assess this.
My horse is tossing its head — is it the bit?
Head tossing can indicate a poorly fitting bit, but it can also be a dental issue, a training problem, or discomfort elsewhere. Always rule out dental problems first before changing the bit. Check fit, width, and thickness before assuming a mouthpiece change is needed.