spring steel and gullet plate, some without). Synthetic materials vary widely in quality. Polyurethane trees are often very well-made, but some cheap saddles are made with fiberglass trees of limited durability. Synthetic trees are often lighter, more durable, and easier to customize. Some designs are intended to be more flexible and move with the horse. Several companies offer flexible trees or adjustable gullets that allow the same saddle to be used on different sizes of horses. Stock Western saddles are saddles originally designed to be used on horses on working cattle ranches in the United States. Used today in a wide variety of western riding activities, they are the "cowboy saddles" familiar to movie viewers, rodeo fans, and those who have gone on tourist trail rides. The Western saddle has no padding of its own, and must be used with a saddle blanket or pad in order to provide a comfortable fit for the horse. It also has sturdier stirrups and uses a cinch rather than a girth. Its most distinctive feature is the horn on the front of the saddle, originally used to dally a lariat when roping cattle. Other nations such as Australia and Argentina have stock saddles that usually do not have a horn, but have other features commonly seen in a western saddle, including a deep seat, high cantle, and heavier leather. The tree of a western saddle is the most critical component, defining the size and shape of the finished product. The tree determines both the width and length of the saddle as it sits on the back of the horse, as well as the length of the seat for the rider, width of the swells (pommel), height of cantle, and, usually, shape of the horn. Traditional trees were made of wood or wood laminate covered with rawhide and this style is still manufactured today, though modern synthetic materials are also used. Leather is stretched and molded around the tree, with minimal padding between the tree and the exterior leather, usually a bit of relatively thin padding on the seat, and a sheepskin cover on the underside of the skirts to prevent chafing and rubbing on the horse. Though a western saddle is often considerably heavier than an English saddle, the tree is designed to spread out the weight of the rider and any equipment the rider may be carrying so that there are fewer