EXHIBIT 10.12.4 US LEC Corp. NON-QUALIFIED STOCK OPTION AGREEMENT

Exhibit 10.12.4

US LEC Corp.

NON-QUALIFIED STOCK OPTION AGREEMENT

THIS NON-QUALIFIED STOCK OPTION AGREEMENT (“Option Agreement”), dated the              day of              , 2006, is issued under and subject to the provisions of the US LEC Corp. 1998 Omnibus Stock Plan as amended (the “Plan”), and is between US LEC Corp., a Delaware corporation (the “Company”), and the undersigned employee of the Company or a Subsidiary (the “Optionee”):

1. Grant of Option . The Company hereby grants to the Optionee, upon and subject to the terms and conditions of the Plan, an option to purchase a total of {xx,xxx} shares of Class A Common Stock of the Company (the “Shares”) at an exercise price of ${xx.xx} per share (the “Option”). The Option is intended to be a non-qualified stock option — that is, it is not an incentive stock option described in section 422 of the Internal Revenue Code (the “Code”) — and this Option Agreement shall be construed to implement that intent.

2. Vesting of Option . Subject to such limitations and restrictions as are provided in the Plan and this Option Agreement, the Option shall vest and become exercisable as to the number of shares set forth opposite the respective vesting dates as set forth on Exhibit A attached hereto and incorporated by reference hereby, provided that the Optionee shall be entitled to cumulate the vested shares and to exercise the same, in whole or in part, after it vests and becomes exercisable, at any time prior to the expiration or termination of the term hereof. Notwithstanding the foregoing, if the Optionee dies while still employed by the Company, the Option shall become fully vested and exercisable in full.

3. Expiration . Subject to the possibility of earlier termination as provided hereafter, all of the Optionee’s rights under this Option Agreement in any event shall expire ten (10) years from the date hereof.

4. Rights upon Retirement . If the Optionee’s employment with the Company or a Subsidiary terminates because of his or her Retirement, and as of such date the Optionee has not exercised this Option as to all of the Shares, the Option may be exercised by the Optionee, to the extent vested under Section 2 as of the date of Retirement, with respect to the vested unpurchased Shares for a period of thirty (30) days from the date of the Optionee’s Retirement. Thereafter, to the extent not exercised, all rights of the Optionee under this Option (other than the Optionee’s right to Shares theretofore purchased under the Option) shall terminate and become null and void immediately.

5. Rights upon Death or Disability . If an Optionee ceases to be employed by the Company or a Subsidiary because of Optionee’s death or Disability and as of the date of such death or Disability the Optionee has not exercised this Option as to all of the Shares, then the Option may be exercised with respect to the unpurchased Shares, provided that the period during which the Option may be so exercised shall expire ninety (90) days from the date of the Optionee’s Disability, if employment ceases on account of Optionee’s Disability, and ninety (90) days from the date of the Optionee’s death, if employment ceases on account of Optionee’s death, and, in the case of Disability, the Option may be so exercised only as to the Shares vested under Section 2 as of the date of Disability. Thereafter, to the extent not exercised, all rights of the Optionee under this Option (other than the Optionee’s right to Shares theretofore purchased under the Option) shall terminate and become null and void immediately. The Option of a deceased Optionee may be exercised by the Optionee’s estate or a person who acquired the right to exercise the Option by bequest or inheritance. The Option of a disabled Optionee may be exercised by a person who acquired the right to exercise the Option by an effective power of attorney or is otherwise authorized to act on behalf of the Optionee.

6. Rights upon Termination of Employment . If an Optionee’s employment by the Company or a Subsidiary is terminated for any reason (by the Company or a Subsidiary whether with or without cause or by resignation by the Optionee) other than by death, Retirement, or Disability, and as of such date the Optionee has not exercised this Option as to all of the Shares, the Option may be exercised by the Optionee, to the extent vested under Section 2 as of the date of termination of employment, with respect to the vested unpurchased Shares for a period of thirty (30) days from the date of the Optionee’s termination of employment. Thereafter, to the extent not exercised, all rights of the Optionee under this Option (other than the Optionee’s right to Shares theretofore purchased under the Option) shall terminate and become null and void immediately.

7. Method of Exercise . The Option shall be exercised by the tender of cash, or, at the discretion of the Committee, by delivery of shares of Common Stock already owned by Optionee or a combination of cash or such shares of Common Stock, or through such other means that the Committee determines are acceptable under the terms of the Plan pursuant to the provisions of Sections 3.2(f) and (g) of the Plan, and delivery to the Committee or Company at its principal place of business of a written notice of exercise, at least five (5) days prior to the date of exercise. The written notice must:

(a) State the election to exercise the Option, the number of whole Shares with respect to which the Option is being exercised (which may not be less than one hundred (100) Shares, unless the number being exercised is the balance of the number of Shares that may be exercised under the Option), the method of exercise elected by the Optionee, and the name, address, and social security number of the person in whose name the stock certificate or certificates for such Shares is to be registered;

(b) contain any such representation and agreements as to Optionee’s investment intent with respect to such Shares as shall be required by the Committee;

(c) be signed by the person entitled to exercise the Option, and if the Option is being exercised by any person or persons other than the Optionee, be accompanied by proof, satisfactory to the Committee, of the right of such person or persons to exercise the Option; and

(d) be delivered by hand or by registered or certified mail, postage pre-paid, return receipt requested, to the Company’s headquarters or to such other location as may be specified in writing by the Company or Committee from time to time.

Within ten (10) days after the Company or Committee receives such notice in a form satisfactory to the Committee and the acceptance of payment, the Company shall deliver to the Optionee a certificate representing the Shares purchased hereunder.

8. Non-Assignability . Except as permitted in section 424(c) of the Code, the Option may not be transferred, assigned, pledged, hypothecated, or otherwise encumbered in any way or be subject to execution, attachment, or similar process. Upon any attempt to so transfer, assign, pledge, hypothecate, or encumber an Option, or upon the levy, by reason of any attachment, or similar process, of any Option contrary to the provisions hereof, such Option shall become null and void. The Committee, in its discretion, may subsequently re-grant to the former Optionee any Option, in whole or in part, which became null and void pursuant to the provisions of this Section 8. If the Option is transferred as permitted by section 424(c) of the Code, the provisions of the Plan, including, but not limited to, the restrictions on transferability, shall apply to the Optionee’s successor, including the executor, administrator, or trustee of his or her estate. Notwithstanding any permitted transfer during the Optionee’s lifetime, during an Optionee’s lifetime the Option may be exercised only by him or her, or by his or her guardian or legal representative.

9. Subject to Plan and Laws . The Option shall be subject to the limitations and restrictions as provided in the Plan, including, but not limited to, the provisions regarding (a) the Optionee’s not being entitled to the privileges of stock ownershi