List of Falcon 9 first-stage boosters

A Falcon 9 first-stage booster is a reusable rocket booster used on the Falcon 9 and Falcon Heavy orbital launch vehicles manufactured by SpaceX. The manufacture of first-stage booster constitutes about 60% of the launch price of a single expended Falcon 9 (and three of them over 80% of the launch price of an expended Falcon Heavy), which led SpaceX to develop a program dedicated to recovery and reuse of these boosters. After multiple attempts, some as early as 2010, at controlling the re-entry of the first stage after its separation from the second stage, the first successful controlled landing of a first stage occurred on December 22, 2015, on the first flight of the Full Thrust version.

Source: Wikipedia — List of Falcon 9 first-stage boosters (CC BY-SA 4.0)