What Does A/R Mean?
The A/R represents the over all inner & outer geometry (shape & size) of the turbo's turbine (hot side) & compressor (cold side) housings. The lager the A/R, the lager the housing. Smaller A/R's bring the boost on faster (less lag) as larger A/R's can yield more over all HP. On our site, you'll often see a option to pick your A/R. The A/R you're choosing is for the turbine housing. (unless otherwise noted) Choosing the best A/R for your needs is critical & can make or brake how the turbo works with your engine. Too small of a A/R can result in a loss of over all power. Overly large & you'll have too much of lag, etc. Two of the same cars, with the same turbo, can have totally different results based on the what A/R was used.

Ha, answered my own question. Google is a powerful thing. lol