Set of 12 Derlin cylindrical bars. Each cylinder is the same diameter, 0.5 (12.5mm) but each has a different length. Set includes a wooden storage block Excellent for physics classrooms. This set allows learners to explore the relationship between density & mass, and how the density of a substance is constant, even as its mass and volume change Designed to be used in an educational setting and are not fabricated using ultra high precision machining. Expect tolerances in the +/- 5% range of any stated dimensions (although they are generally much tighter). educational setting and are not fabricated using ultra high precision machining. Expect tolerances in the +/- 5% range of any stated dimensions (although they are generally much tighter). The Eisco Labs Density Investigation series is intended to help learners become familiar with a variety of common substances, explore volume, density & mass and provide them with quality introductory physics and chemistry concepts UPC 849230057886 Brand Name EISCO Item Weight 12 ounces Manufacturer Eisco Model Number PH0113K Material Type Wood Item Dimensions 4 x 3.5 x 4 inches Manufacturer Part Number PH0113K