On May 14, 2010, the Bruker Corporation 2010 Incentive Compensation Plan (2010 Plan) was approved by the Company's stockholders. The 2010 Plan provided for the issuance of up to 8,000,000 shares of the Company's common stock. The 2010 Plan allowed a committee of the Board of Directors (Compensation Committee) to grant incentive stock options, non-qualified stock options and restricted stock awards. The Compensation Committee had the authority to determine which employees would receive the awards, the amount of the awards and other terms and conditions of any awards. Awards granted under the 2010 Plan typically were made subject to a vesting period of three to five years.

On May 20, 2016, the Bruker Corporation 2016 Incentive Compensation Plan (2016 Plan) was approved by the Company's stockholders. With the approval of the 2016 Plan, no further grants have been made under the 2010 Plan. The 2016 Plan provides for the issuance of up to 9,500,000 shares of the Company's common stock and permits the grant of awards of non-qualified stock options, incentive stock options, stock appreciation rights, restricted stock, unrestricted stock, restricted stock units, performance shares and performance units, as well as cash-based awards. The 2016 Plan is administered by the Compensation Committee. The Compensation Committee has the authority to determine which employees will receive awards, the amount of any awards, and other terms and conditions of such awards. Awards granted under the 2016 Plan typically vest over a period of one to four years.

The Company recorded stock-based compensation expense as follows in the unaudited condensed consolidated statements of income and comprehensive income (dollars in millions):

In addition to the awards above, the Company recorded stock-based compensation expense of $0.4 million and $0.8 million in the three and six months ended June 30, 2019, respectively, related to the 2018 acquisition of Mestrelab Research, S.L. (Mestrelab).

Stock-based compensation expense is recognized on a straight-line basis over the underlying requisite service period of the stock-based award.

Stock options to purchase the Company's common stock are periodically awarded to executive officers and other employees of the Company subject to a vesting period of three to four years. The fair value of each option award is estimated on the date of grant using the Black-Scholes option-pricing model. There were no stock options awarded during the three and six months ended June 30, 2019 and 2018.

(a)	In addition to the options that are vested at June 30, 2019, the Company expects a portion of the unvested options to vest in the future. Options expected to vest in the future are determined by applying an estimated forfeiture rate to the options that are unvested as of June 30, 2019.

(b)	The aggregate intrinsic value is based on the positive difference between the fair value of the Company’s common stock price of $49.95 on June 30, 2019 and the exercise price of the underlying stock options.

The total intrinsic value of options exercised was $6.9 million and $5.3 million for the six months ended June 30, 2019 and 2018, respectively.

There was no restricted stock award activity for the six months ended June 30, 2019.

The total fair value of restricted stock awards vested was $0.2 million in the six months ended June 30, 2018.

Restricted stock unit activity for the six months ended June 30, 2019 was as follows:


		Weighted
		Average Grant
	Shares Subject	Date Fair
	to Restriction	Value
Outstanding at December 31, 2018	806,249	$	29.88
Granted	43,282		30.95
Vested	(39,282)		34.81
Forfeited	(24,303)		29.43
Outstanding at June 30, 2019	785,946	$	29.71

The total fair value of restricted stock units vested was $1.4 million and $1.1 million for the six months ended June 30, 2019 and 2018, respectively.

At June 30, 2019, the Company expects to recognize pre-tax stock-based compensation expense of $2.8 million associated with outstanding stock option awards granted under the Company's stock plans over the weighted average remaining service period of 1.9 years. The Company expects to recognize additional pre-tax stock-based compensation expense of $0.1 million associated with outstanding restricted stock awards granted under the Company's stock plans over the weighted average remaining service period of 0.1 year. The Company also expects to recognize additional pre-tax stock-based compensation expense of $15.7 million associated with outstanding restricted stock units granted under the 2016 Plan over the weighted average remaining service period of 2.6 years.