A 16mm Saddlery roller buckle is a small-sized buckle typically used in the making of equestrian products such as horse riding gear, belts, and saddles. It is made of durable materials such as brass, stainless steel, or nickel-plated steel, and is designed with a roller mechanism that allows the belt or strap to move smoothly through the buckle. The roller also helps to reduce wear and tear on the leather or fabric by reducing friction. The buckle is typically secured to the belt or strap by a prong and a loop, ensuring a secure fit.