How do i know if ugg's on ebay are real?

I just bought some from another retailer- a fabric from New Zealand- the real deal without the UGG logo and half the price only.. looking forward to receive them
got the tip from a friend as to me it's not important to have the logo on but want good quality first
hope the keep their promises
 
Sabine, as far as I know uggs have three markings:
-a tag on the inside with the type of leather/shearing, location made, and some sort of serial number
-an imprint on the bottom, different from style to style
-a mark on the back of the heel that's visible that sats ugg australia.

the walking store, norstroms, and a few others are carrying uggs if you want to see them irl first. the marks may be different from style to style... what uggs are you looking at?
 
I'm looking at the classic tall one's. I already have them but i got a bad feeling about them when i was looking on Ebay. I live in Holland and ugg's are elly exspensive here