Difference between Promote with no cap and Promote with customized cap

[ansar30]

Hello there, I'm a new seller. I've got the feature promoted gigs. When I want to set a CPC, I see two option Promote with no cap and Promote with customized cap. Now, the question is which one should I select Promote with no cap or Promote with customized cap? And another question is which one will be best for me. Thank you. 

[lloydsolutions]

 

[sayfdesigns]

Hi Same question please,