Abstract: This invention relates to a piston with its skirt being cut to locate four sets of bearing pads and circulating bearing balls. Each pad has been milled to have a doughnut shaped groove with half of a circle cross-section to hold the ball bearing in circulation during the piston reciprocating motion. Two lines of bearing balls on each side of a piston pin are in contact with the cylinder liner and share the piston thrust load. Lubrication of the ball bearings is ensured by oil slots through the piston skirt under the oil ring groove to the top of the grooves of the bearing pads and to the exposed bearing balls in rolling contact.