Horse split leather reins are reins made from split leather, which is a type of leather that has been split from the top grain layer. Split leather is usually softer and more flexible than full grain leather, making it a popular choice for reins. These reins are often used in horse riding and training, as they provide a good grip and are comfortable for both the rider and the horse. Split leather reins are durable and long-lasting, making them a practical choice for everyday use.