Follow-On Offering
  
See: Follow On Public Offer. See: Secondary Offering.
You already went public via your IPO. But now you have insiders who want to sell. They'll do a secondary offering, otherwise known as a follow-on offering, usually within a relatively short time from when the IPO hit. Via the 144a Regulations, insiders must hold their stock 6 months and change before being allowed to then dump them, er, um...sell them to the public. It's usually at that time that the follow-on offerings happen.