Top End Kit: 010-834-12 .50MM Over (789cc), 71.80mm Bore. Fits: POLARIS 780. Made to exact OEM specifications Top End Kits Include: Pistons, Rings, Wrist Pins, Circlips, Top End Bearings, Head, Base, Common Intake and Exhaust Gaskets required for rebuilding the top end of the motor**Prior to placing your order please measure your cylinders to determine the appropriate size required. Most pistons come in .25mm increments from stock or standard bore up to 1mm oversize. Refer to your shop service manual for guidance on the procedure or have the cylinders evaluated by a qualified machine shop**