I purchased this to add to a moisturiser to provide a light coverage to my daily look rather than bothering with makeup on my days off but I honestly used it probably twice then forgot or just couldn't be bothered as I have a few BB and CC creams just found it relatively useless.
It does give a nice hue of colour that if you get the correct shade matches your natural skin tone and gives you a moistured tint the same as any BB, CC or tinted moisturiser does so for the price, hard to find in NZ aspect I wouldn't bother with these custom drops to be honest.
This is quite pricy and you don't get a lot, but if you manage to get it on sale it is well worth it! Just one drop makes a massive difference.
It mixes really well with all sorts of foundations, and not only gives it more coverage but also helps it blend further. I definitely feel like you could use a lot less foundation, when you add a drop of this. it doesn't detract from the finish of the foundation, but it can extend the wear, and it doesn't crease when used under the eyes.
It also mixes well with a sunblock or a thick moisturiser or primer, it also works with thin consistencies, just not as well as thicker ones. It can be used on its own, but the finish is not as flawless, and it can be a bit harder to blend out, I guess because its made to be diluted.
Tips: A darker colour and a lighter colour of these drops are useful to have - you can turn your foundation into contour/concealer, or adjust a foundation you already have to suit your skin tone.
I like to use a teeny tiny dot of this, in a colour that matches me, on small blemishes that hard to cover, especially on days when I'm not wearing much makeup - it looks invisible when its used to spot -conceal