Oem big bore cylinder 72mm with cut oem head. Cylinder is ported for mid to top end has a really nice port work. Unknown porter has a number on bottom of cylinder from porter. Number is 15269. Bore is at 72mm firs bore on the cylinder. Cylinder is in ok shape I have done a light hone with a stone hone and cleaned up good needs a final hone with ball hone. Could be used with just a piston and hone but will leave it up to the buyer. $150 obo update