Abstract: This invention provides non-destructive testing of elongate compressible materials, and particularly to determine the elastodynamic properties of a material, and/or to detect defects such as non-uniformities in resilience or hardness, subsurface as well as surface defects such as inclusions, voids, tears, and the like. The material to be tested is passed between two rollers of substantially contant roller spacing. Measurement of the load provides an indication of elastodynamic properties of the material. Variations in the measured load can be utilized to detect defects in the material. The invention has been found particularly suitable for the testing of material for seals, such as O-rings.