MAC Aeros Blue is a very cool-toned, medium-dark blue with a satin finish. It is a limited edition eyeliner that retails for $16.00 and contains 0.1 oz.
MAC Aeros Blue Pro Longwear Fluidline ($17.00 for 0.10 oz.) is a bright, medium-dark blue with strong, cool undertones and a satin sheen. It had medium coverage in a single stroke, and it was buildable to semi-opaque coverage.
The formula is supposed to have 8-hour wear and be waterproof and smudge-proof. I found the the texture to be very emollient, which made it difficult to build up color or get really thin, even lines (I used MAC's 266 brush in the swatch and in practice). It would actually work better as an eyeshadow base for that very reason rather than an eyeliner (where even, opaque coverage is typically more ideal). It did wear for over ten hours on me, though.