ピストンリングは「The rings on this piston are tapered & only fit one way up.
」で「Unfortunately there are no markings on the rings and they are different. One ring is tapered (top ring) and the bottom ring is parallel. You should be able to make out the taper ring visually, if not use a vernier gauge. The taper side goes to the top of the top ring.」とのことです。