Initial Options granted to Non-Employee Directors shall become exercisable over four years, with one-fourth of the shares subject to such Initial Options vesting on the first anniversary of the date of grant and the remaining shares subject to such Initial Options vesting in thirty-six equal monthly installments over the three years thereafter, such that each Initial Option shall be 100% vested on the fourth anniversary of the date of grant, subject to the director’s continuing service on the Board through such dates. Subsequent Options granted to Non-Employee Directors shall become vested in twelve equal monthly installments of one-twelfth of the shares subject to such option on the first day of each calendar month following the date of the Subsequent Option grant, subject to a director’s continuing service on the Board through such dates. Unless otherwise determined by the Board, no portion of an option which is unexercisable at the time of a Non-Employee Director’s termination of membership on the Board shall thereafter become exercisable. All Initial Options and Subsequent Options granted to the Non-Employee Directors shall vest in full immediately prior to the occurrence of a Covered Transaction (as defined in the 2012 Plan).