The two-rein stage is where you start to transition into the bridle with your horse. Since he's learned to respond to the hackamore, you keep him in a smaller version of one, the bosalito, while you let him get used to carrying the bit. Slowly but surely, you'll start to work more and more from the bit, but if you ever need to pull on the horse, you've still got the bosal to do it with. You never want to pull on them with a bit! Of course with the bosalito you'll need a smaller mecate as well and this little 3/8" one will work just great for you.