I pretty much collect the MAC fluidlines, because other than lipsticks, gel eyeliner is my weakness, and MAC has my favorite formula of them all.
Rich Ground is a gorgeous, true copper shade, shot through with a bit of red, and imbued with the perfect amount of shimmer. "Rich" is definitely the adjective that first comes to mind when I use this product. I have brown eyes and it does a great job of brightening them up, but I can only imagine what sort of magic this eyeliner does for those with blue or hazel eyes especially.
The formula is the "good" kind of Fluidline (I mean that in the way how some Fluidlines are really pigmented and creamy, and others sort of sheer out when applied). It's very smooth, densely saturated with color, and does not require any layering at all. The lasting power (as with other Fluidlines) is magnificent and it stays on flawlessly all day on my oily, hooded lids with a bit of primer and powder, of course.
If you're into eyeliners like I am, I definitely recommend you try this one out. It's foolproof, an amazing value for the money, and the little pot will last you forever because you don't need to go back and reapply. 10/10.