YSL Touche eclat is the absolute creme de la creme of under eye concealers and one I like to treat myself to when I can afford it.
It isn't cheap to buy at around £24 for a small 2.5ml pen. What it does is highlight the under eye area bouncing off shadows and making bags and dark shadows dissapear.

The packaging is lovely and it's clear you are buying a quality product. It comes in it's own box and inside is the applicator pen which is gold coloured. Once you remove the lid you will see the applicator brush which is where the product comes out and you do this by clicking the pen.

A couple of clicks will give you enough product to do both eyes and what I do is just dab some on the inside corners and dab my way out to cover my whole eye area.
I find that applying some heavier concealer first covers up all the blemishes I want hidden and then the Touche Ecalt just lightens and brightens the areas perfectly finsihing it off.
I have tried using it on it's own but I just don't think it is heavy enough to actually cover really dark circles and the evidence of late nights and I find it is much better as just a highlighter than an actual concealer.

You can buy Touche Eclat in 3 different shades and I use no2 as no1 is for the really pale and no3 is for darker skin tones and I would say I am probably a medium. I am white but a black girlfriend of mine swears by the no3 which is light peach and says it does wonders for her skin even though to look at it you would think it would be to light for black skin so it may be worth trying if you are looking to find the perfect concealer/highlighter.

Touche Eclat is a brilliant product and one that I ufortunately go through far to quickly when I have it. Because it is so expensive for such a small amount it is not something I can afford to buy regularaly and m boots concealer does me fine the rest of the ime but if I win the lottery I will definately be using this on a daily basis.