How can I tell if my benefit cosmetics I bought from ebay are fake?

Can anyone give me a definitive answer? I bought brows a gogo, an 'It' foundation stick and travel size 2.5ml highbeam, moonbeam and stayput. I have checked out the youtube videos and I'm still not sure, I don't want to pull apart the packaging on the eyebrow kit to check. I did expect the consistency of the brows a gogo makeup to be better than it is. ie not the highlighters are 'sticky'. Thanks.