Various manufactures have different designs.
Usually rings are "barrel" shaped on the edge that contacts the cylinder.
The 45* chamfer is usually referred to when speaking of the inside of the ring that lives in the piston groove, and that usually faces to the top of the piston.
It is felt the 45* bevel promotes better sealing when the explosion occurs in the cylinder, forcing the ring tighter to the cylinder wall.
Usually the 45* chamfer is 2nd ring and a non marked ring or "barrel" outside edge is the top ring.
Some top rings are chrome edge or have a moly overlay.
Second rings are most always grey cast iron.
As mentioned, ring manufactures instructions always take preference.
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