These cubes are highly compressed timothy hay. The hay is dryed, chopped and compressed, then sold by the bag. Some people replace a portion of their horse's hay with hay cubes and they are useful if your horse can't tolerate even a small amount of hay dust. These cubes are very hard, and while a horse's jaw is very strong, there is a chance of choke. Soaking and breaking up the cubes is one way to avoid this problem.