Product Properties: The steel ball is made of AISI1015 carbon steel, the size is 1/2inch(12.7mm). The weight of each steel ball is about 0.835g, it's surface is smooth. Product Advantage:The precision bearing steel ball is for professional slingshot competition, it makes the flight more stable.And it can easily lock the objects nearby due to it 's big size and weight so that you could hit the target more accurate and more powerful. It is very suitable for professionals.