This is a really nice example of the Frank Baines Reflex dressage saddle. This has a 17.5ins seat with a medium* gullet (as stamped), but we measured the gullet to be 4ins and would regard this more as a narrow/medium fit, as not a generous medium. The saddle flaps measure 16ins in depth.
This is what Frank Baines’ says about its Reflex dressage saddle:
For a really close contact, the Frank Baines’ Reflex dressage saddle is a serious consideration. It comes with a choice of two knee blocks (only one set provided with this particular saddle), which you can fit to your own requirements and a cut-away sweat flap, acting as a monoflap saddle.
Frank Baines Reflex Dressage Saddle helps put you in the classic dressage position giving you the closest possible leg contact with your horse. With the most comfortable seat imaginable, it makes this saddle a complete pleasure to ride in. A single flap system allows the rider to feel extreme contact with the horse and its movements and a thinly flocked pure wool panel also adds to the contact you will feel when riding. A concealed V girthing system eliminates bulk under the riders leg and helps minimize movement and a contoured Velcro knee block offers the option to alter the position and size of block to suit your needs.