What MAC say: "A luxurious domed face powder with minerals, slowly baked to provide a dimensional yet natural-matte finish. Provides perfect low coverage. Use to set and fix foundation or as a touch up throughout the day"
I came across this when I went to a MAC counter to by a new Studio Fix Powder. I use powders after applying foundation to set the foundation in place and prevent shine. I therefore only use it on oily areas (T-Zone) to avoid looking too matte (and unhealthy). However, I'd been thinking this combination was making my face look too heavy, and the assistant introduced me to this. It does the job perfectly.
It basically gives a finishing touch to your foundation. Because it has a very slight sparkle to it, your face doesn't look to cakey and it maintains a bit of a glow. It prevents my make up slipping and face becoming oily ALL DAY.
There are a nice variety of shades on offer, but I'd recommend going into the shop and having a real good test as weirdly some of the medium colours look lighter than the light ones.
It's not cheap at £20.50, but it's worth it.
For more details and to buy online: