Ampa- The term 'abc' means aluminum brass chrome plated. Aluminum piston, and brass liner that is chrome plated.

ABN refers to sleeves that are nickel plated.

AAC means the process that Saito uses for aluminum piston, aluminum cylinder (no sleeve), and is chrome plated.

You can have abc ringed engines. The difference between ringed abc and nonringed abc engines is the pinch in the sleeve for nonringed engines. The top is slightly smaller in diameter. This pinch gives the cylinder compression at the top of its stroke. Most two stroke engines are ABC and nonringed.

A Kange is both ringed and with a pinch.