Rice Lake Cast Iron ASTM Class 7 Round Slotted Interlocking Counterpoise Test Weight, 50lbs x 1/2lbs Mass U.S. customary slotted, interlocking counterpoise weight for use with counterpoise weight hangers Painted cast iron weight has chip-resistant paint that resists corrosion and conforms to NIST Handbook 105-1 standard Sealable adjusting cavity for adjusting total weight Meets American Society for Testing and Materials (ASTM) E617, Class 7 specification for rough weighing operations in physical and chemical laboratories, and for force-measuring apparatus