Traditionally, the tree of an English saddle is built of laminated layers of high quality wood reinforced with spring steel along its length, with a riveted gullet plate.
For example, a close contact style of English saddle, designed for show jumping, places the rider's seat farther forward than does a dressage style English saddle.
Dressage saddles have longer billets and use shorter girth than other types of English saddles to minimize the straps and buckles underneath the rider's legs.
The proper way to measure the seat size of an English saddle is diagonally from either saddle nail, on the side of the pommel, to the centre of the cantle.