The vial states for every 1ml there is 350 mg after reconstitution. The 2.1 is listed on the vial. DIRECTIONS FOR USE: Intramuscular Administration: Reconstitute Rocephin powder with the appropriate diluent (see COMPATIBILITY AND STABILITY). Inject diluent into vial, shake vial thoroughly to form solution. Withdraw entire contents of vial into syringe to equal total labeled dose. After reconstitution, each 1 mL of solution contains approximately 250 mg or 350 mg.