The O2ptima CM Checklist app simplifies rebreather assembly with dedicated checklists mirroring the manual lists. Set precise countdown timers for Positive, Negative, and Pre-breathes. Summary view of your build with caution blocks if steps are missed. Manage your build from a simple digital checklist! Help save the planet by moving away from throw away paper every time you dive to a digital checklist in your phone or Ipad!