An economical set of 12 drilled balls for all your pendulum experiments. Set contains two each 25mm diameter balls of brass, aluminum, steel, wood, cork, and copper, in a plastic box for easy storage. All drilled balls feature 3mm countersunk holes so pendulum cord knots can be recessed. Additional Info: An set of 12 drilled balls for all your pendulum experiments. Set contains 2 each 25mm balls of brass, aluminum, steel, wood, cork, and copper, in a plastic box for easy storage. Feature 3mm countersunk holes so pendulum cord knots can be recessed. Package Size(L x W x H): 7.5 X 4 X 1.5 (IN) Categories: Mechanics, Pendulum Balls HTS Code: 9023.00.0000 UNSPSC: 6.01e+007 Country Of Origin: INDIA