Measuring the dynamic behavior of materials using the traditional Kolsky bar apparatus involves specifying the specimen to be tested. The dimensions, and associated tolerances, of the specimen are two of the many variables that must be specified for a test. The goal of specifying the dimensions and tolerances of the specimen is to ensure that any variations in the specimen fabrication do not produce unnecessary variations in the results. Requiring conformance to fabrication specifications, expressed by using international standard formats, can ensure that reproducible results, independent of the fabrication shop, are obtained. Appropriate dimensions and tolerances, and approaches for specifying them, are discussed in this SEM conference paper.