Compression platens are made up of alloy steel with minimum hardness of 55 HRC. The flatness tolerance is 0.03 mm and the roughness value (Ra) is in the range of 0.4 μm. The spherical seat, in lubricating oil enclosure, allows initial free alignment when the initial contact with the specimen occurs and automatically locks in this position up to the termination of the compression tests as required by the standards.