Questions about advertisers directly buy traffic from publishers

Monetizing, Advertising & Marketing Advertising Networks
1

Hi, guys
Do you know what mobile ad platform have this kind of market that advertisers can directly buy ads from publishers?
Please give me some recommendation!
Thanks a lot!
:smiley:

2

Chartboost, Appnext seems having it.

3

Ok, Thanks! Dude

4

Except Chartboost, Appnext, anyone can give more recommendation?
Thank you!