Hardware support for software controlled reconfiguration of performance counters may include a plurality of performance counters collecting one or more counts of one or more selected activities. A system is provided comprising a hub cap, a target coupled to the hub cap, and at least two displacement sensors configured to measure a displacement between each displacement sensor and the target. A gate is fowled over the tunnel dielectric layer. Air can be injected into the toroidal tube so as to conform the face of the patient. The first part is also in contact with a spring.