Now to be perfectly honest I've never really "got" the whole Mac thing, Ive tried a few of their products and liked them but at my local store I find the staff rather unhelpful and abit intimidating so I've been kind of put off. However, I bought these brushes online and the service was bloody amazing, haha, really short sign up form and then they were delivered in 2 days, and all for about £3, which is cheaper than getting to my nearest Mac store.
The 217 brush its self is absolutely hands down the best thing I have ever bought from Mac, and certainly the best brush I have ever bought. Its used for blending colours together, and really good for blending darker colours into the crease line of the eye. The brush is really soft and hardly removes any colour so it spreads really well.
If you are trying to create blended or contoured eyes or looking for a good starting brush for your kit its most definitely worth the money. Watch this space for the other 2 brushes I bought...