This excerpt taken from the DXCM DEF 14A filed Apr 12, 2006.
Limitations on ISOs. The aggregate Fair Market Value (determined as of the date of grant) of Shares with respect to which ISOs are exercisable for the first time by a Participant during any calendar
year (under the Plan or under any other incentive stock option plan of the Company or any Parent or Subsidiary) shall not exceed $100,000. If the Fair Market Value of Shares on the date of grant with respect to which ISOs are exercisable for the first time by a Participant during any calendar year exceeds $100,000, the Options for the first $100,000 worth of Shares to become exercisable in that calendar year will be ISOs, and the Options for the Shares with a Fair Market Value in excess of $100,000 that become exercisable in that calendar year will be NSOs. If the Code is amended to provide for a different limit on the Fair Market Value of Shares permitted to be subject to ISOs, such different limit shall be automatically incorporated into the Plan and will apply to any Options granted after the effective date of the Codes amendment.