I recently purchased this product off sephora after I heard so many youtubers raving about it. Although this bottle is small, the product inside is super pigmented. I got the shade G20, as in Winter my skin fades from bronze goddess, to jaundiced. So all my favourite foundations need a little lightening love.
The product comes in a tiny bottle with a dropper dispenser, which makes using the product all that easier. This product blends nicely into the foundation without changing the texture or finish of the product. It makes customising your foundation so much easier, just a few drops and your foundation goes from just cake to icing on top of cake as well (which I love). So if you're into a light coverage product whack some of this into some moisturiser and you'll be good to go.
The fact that there are so many different undertones in the shade range and a little goes a long way, this product is definitely a keeper. My only worry is that with so many shades being suited for every skin tone in the middle, super pale or dark girls might miss out. Cover FX may widen the shade range with time, but if you find one that will suit you snap that little bottle of goodness right up.
They're expensive, for sure, but for what is essentially pure pigment in a very useful format, I think it's worth it. I have G30 and I add a couple of drops to sheer products to dial up the coverage level. I've also used them to adjust the undertone of very pink-toned foundations to suit me better (I'm more of a neutral tone). The bottle is a little bit less than ideal because a) it's glass and b) the dropper can get a little messy, but I just handle with care and haven't made too much of a mess yet.
Tips: Search online thoroughly for swatches before you commit to a shade.