The most remarkable piece of technology is certainly the airbearing slider that carries the read/write elements within just a couple of nanometers clearance above the disk surface. Numerous analogies have been made: for example, scaling the disk up to the size of the United States, the slider would be about 40 miles long and the clearance would be 1/8 in. The read/write heads are at or very close to the lowest point on the slider. The exact clearance is set by using a thermal actuator (tiny resistive heater) on the slider. Thermal expansion is used to move the read/write heads down towards the disk surface by several nanometers until just sufficiently small clearance is obtained. It is interesting to note that the physical clearance is now a relatively small item in the total magnetic spacing budget, with items like the protective overcoats on the head and disk taking up a larger portion of the total budget.