I needed really fine highlighters for my sister in law's wedding when I did her and the bridesmaids' makeup. I did a post on all the makeup I used if you are interested. I bought the sample size kit for $20 from Ulta. Of course the full size product would buy me more product per dollar, but I think the sample sizes will probably last forever.
I got the liquid version in two different packages. The tube version was a sample that came from Ulta, not with the kit. I think they are the exact same product. Let me know if I am wrong. I really loved all of them. They are finely milled to the point that you can only see them on the skin when light it. I think that is the most natural way you can do highlighting on daily bases.
Opal has really nice nude tint with sun kissed pink undertone. I used the liquid one first then topped it off with the powder. I thought the color payoff was slightly better with liquid formula, but the powder formula was much more natural. However, I can see them being bit over the top on people with darker skin tone, so it might be better to check out other colors from the range. Overall, I absolutely adore these guys and would totally buy them in full size if I run out of them.