Pre-ping is a real time inquiry via API to see if a lead is a duplicate in your database before the display of your offer. 

The main advantage to utilizing a Pre-ping is to give a lead provider an opportunity to know if a lead already exists in your database before displaying your offer. Pre-ping should substantially reduce, or completely eliminate, the number of duplicate leads that are attempted to be sold, reducing the amount of unsold leads from the lead generator.

If you have a large database of clients, the number of dupes you receive from lead buys can be substantial. This can cost your providers a great deal of money, and they may be less inclined to run your offer without the availability of a pre-ping.