For the platen sliding system, the LHPOST uses six MTS Model 270 Style vertical pressure balance bearings to react against the vertical forces imposed by the platen, the specimen, the discrete prestressing overturning moment system hold-down force, additional gravity loads, and the overturning moments from test specimens. These pressure balance bearings are very efficient at high capacities. The high-pressure capability allows for minimum size. The seals minimize leakage and zero power is required for flow. The bearings are self-aligning up to 2 degrees, low in friction, can operate at high velocities and high strokes, use servo-control, which allows height adjustment to provide alignment, and can also function as actuators. The bearings have a force capacity of 9.4 MN and a stroke of ± 13 mm.