Innovation 2026
Equation saddle by Gaston Mercier

One saddle. One concept. Endless solutionsThe perfect fit

Discover the Equation Saddle on video

The Equation saddle

Designed for horse and rider together, adaptable to the way you ride.

Gaston Mercier
Saddle designer and maker

The Equation saddle is the modular, adjustable and interchangeable saddle by Sellerie Gaston Mercier. Front and rear panels that move, interchangeable flocking, an adjustable and interchangeable seat, interchangeable flaps, and tree bars that are free and independent on the right and left: every part adapts.

One saddle, fitted to your horse’s back over time, with interchangeable flaps and seat to move from dressage to jumping, from flatwork to hacking.

Your horse keeps its bearings, you keep your seat. It was born in our workshop in Aveyron, France, from hands that cut, stitch and build leather the way it has always been done.

Book an appointment →
The Equation principle

A patented base, everything else adapts.

Tree size, seat size, panels, flocking and flaps: everything is interchangeable. At the first appointment, our saddle fitter sets the base to your horse’s back; you then build your saddle around the way you ride.

Adjusting the saddle with the knob
AdjustableAdjustable seat, front and rear panels that move: a saddle that evolves with you.
Saddle components on their base
ModularSeparate components assembled on a patented base: tree, seat, panels, flaps.
Fitting the seat onto the base
InterchangeableFlaps, seat and flocking can be changed easily by the rider.
Underside of the Equation saddle: independent right and left tree bars
Free & independentIndependent right and left tree bars, for freedom of the horse’s back.
Interchangeable flaps

7 configurations, one single saddle.

From dressage to endurance, choose the flaps that suit your riding.

Equation saddle on its stand, interchangeable flaps on the fence
One base, flaps to change for the way you ride
Flap General purpose Muze
01MuzeGeneral purpose
Flap Trail endurance Margeride
02MargerideTrail · endurance
Flap Dressage Doline II
03Doline IIDressage
Flap Dressage Doline III
04Doline IIIDressage
Flap Endurance Florac 2.0
05Florac 2.0Endurance
Flap General purpose Compiègne
06CompiègneGeneral purpose
Flap Jumping cross GP · D13
07GP · D13Jumping · cross
Your configuration

A saddle fitter helps you choose the right flaps for the way you ride.

Book an appointment
In action

Your horse keeps its bearings, you keep your seat.

One saddle, fitted to your horse’s back, from flatwork to jumping.

Rider jumping with the Equation saddle
Jumping
Rider on the Equation saddle
Flatwork
Close-up of the Equation saddle on the horse’s back, Gaston Mercier badge
Close to the back
Try the Equation saddle
The Gaston Mercier saddlery team in the workshop
Adjusting the panels of the Equation saddle
The Equation saddle on its stand, close-up of seat and leather
The saddler at work
Frequently asked questions

All about the Equation saddle

What is the Equation saddle?

The Equation saddle is the modular, adjustable and interchangeable saddle by Sellerie Gaston Mercier. A single saddle adapts to your horse’s back, your build and your riding: panels, flocking, seat, flaps and tree bars can be adjusted or swapped. It is handmade in our workshop in Aveyron, France.

What is the difference between adjustable, modular and interchangeable?

Adjustable: the saddle can be set up (seat position, front and rear panel mobility). Modular: it is made of separate components assembled on a base. Interchangeable: each component (flaps, seat, flocking) can be replaced by another, depending on the horse, the rider or the discipline.

Which parts of the saddle can be adjusted or changed?

The panels move at the front and at the back, and their flocking is interchangeable (length, thickness, density). The seat is adjustable and interchangeable. The flaps are interchangeable depending on the discipline. The tree bars give freedom and independence on the right and left sides.

Why independent tree bars on the right and left?

A horse’s back is never perfectly symmetrical. Independent right and left tree bars give the horse’s back more freedom and allow a finer fit, for the horse’s comfort and the rider’s balance.

Can I change the flaps myself?

Yes. The flaps are screwed on and can be changed easily by the rider, without touching the base settings. You can switch from dressage to jumping, from flatwork to hacking.

Which disciplines is the Equation saddle suited to?

Seven flap configurations are currently available: dressage (Doline II, Doline III), jumping and cross-country (D13), general purpose (Muze, Compiègne), trail and endurance (Margeride) and endurance (Florac 2.0).

Will the saddle adapt if my horse changes?

Yes, that is the whole point of the Equation saddle: it adjusts over time. When your horse’s back changes, or if you change horse, the panels, flocking and tree size can be modified without buying a whole new saddle.

How can I try the Equation saddle?

Book a personalised saddle assessment: a saddle fitter comes to you and sets the base to your horse’s back at the first appointment. You can also try it at our test centre, Le Mas de Vinaigre, Saint-Léons (Aveyron, France), by appointment.

Try it

Come and try it, or we come to you.

Personalised saddle assessment

Appointment with a saddle fitter

Our fitter comes to you, assesses your horse and recommends the right configuration. At the first appointment, the base is set to your horse’s back.

Book an appointment
Test centre

At Le Mas de Vinaigre, Aveyron, France

In our test centre, inside the workshop, ride the Equation saddle, swap the flaps and feel the difference. By appointment.

Sellerie Gaston Mercier
393 Route du Mas de Vinaigre, Le Mas de Vinaigre
12780 Saint-Léons, France · +33 5 65 47 60 98
contact@gaston-mercier.com
The best way to understand it is to sit in it.
Gaston Mercier, saddle designer and maker
Designed and handmade in Aveyron, France
La juste mesure