Jennifer Aniston is a friend who will definitely be there for you - and your beauty needs. The Hollywood actress admits that she loves to test new hair products on her friends - like real-life Barbie Dolls.

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According to People Magazine on Wednesday, the Cake star says that her friends volunteer to be guinea pigs for her new haircare line before they hit store shelves.

She said, "Chris [her hairstylist] and I usually get samples like six months before so we get to try it out and see how it lasts over time and then give feedback for it."

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She also said that she likes to try out the samples on her famous friends like Courteney Cox and yoga instructor Mandy Ingber.

Aniston added, "They allow me to sort of use their hair, they're like Barbie dolls," she says. "Courteney has gorgeous hair, and Mandy's is really curly so she loves the No Frizz line. Plus, everything smells incredible, that's my other thing that I love about these products. For me that's always a big thing, that it isn't too fragrant-y or perfume-y. It's so fresh and so light, so incredible."

As far as her favorite product, Aniston says it's the Night Cap Overnight Perfector.

She said, "I'm in love with it. When they said to me,' Okay, you put it on your hair at night.' And I said, 'So I'm going to put a cream on my hair right before I go to bed, and I'm supposed to wake up loving it?' And honestly, I don't know what they did or how they did it, but I woke up in the morning and my hair was so shiny and vibrant and the color looked great and it wasn't dirty or greasy and there wasn't a spot on my pillow. I don't understand it. It's kind of like magic."

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