ORIGINAL: William Robison

AAC is a variant on ABC, substituting aluminum for the brass sleeve. Same characteristics as ABC.

ABN is a cheap variation on ABC, instead of using a chrome plating it has nickel plating on the sleeve. Thunder Tiger has given excellent service with ABN, and their selling price is low, probably in a large part because of the inexpensive ABN process. OS. the other current user of ABN, has a continuing problem with failure of the plating which effectively ruins the engine due to the excessive price of repair parts. Side note: The OS engines with ringed pistons are still of good quality and long engine life. ABN is cheap to make, and is easily damaged.