Some tension specimens are machined by cutting threads on the rod ends and reducing the diameter between the threaded ends. Threads of this sort are called upset threads. Since the rod diameter at the ends is larger than the specimen diameter, the presence of the threads does not reduce the strength of the specimen. Tension specimens with upset threads are attached to the testing machine with threaded specimen holders, which eliminate any possibility that the specimen will slip or pull out of the grips during the test.