A good fit for an english style saddle is when you sit in the saddle and you still have a hand's width of space behind your back and the tip of the cantle. The saddle should not be too wide nor too narrow. If you have too much or too little space, you're going to feel uncomfortable and riding might not be as much fun as it should be. Therefore, when buying a saddle, first make sure it is a good fit and comfortable for you so you can enjoy your time while riding.