Note 13. Stockholders’ Equity and Stock-Based Compensation

Options and Employee Stock Purchase Plan (“ESPP”) Awards

The fair value of each option and ESPP award is estimated on the grant date using the Black-Scholes valuation model and the assumptions noted in the following table. The expected lives of options granted were calculated using the simplified method allowed by the SAB 107. The risk-free rates were based on the U.S Treasury rates in effect during the corresponding period of grant. The expected volatility was based on the historical volatility of the Company’s stock price. The dividend yield reflects that the Company has not paid any cash dividends since inception and does not intend to pay any cash dividends in the foreseeable future.

	March 26, 2016			March 28, 2015
Employee Stock Purchase Plan:
Expected life	0.5 years			0.5 years
Volatility		39.1	%		37.2	%
Risk free interest rate		0.49	%		0.11	%
Dividends		—			—

No stock options were awarded during the three months ended March 26, 2016 and March 28, 2015, respectively.

A summary of activity of stock options during the three months ended March 26, 2016 is as follows:

	Number of Shares Outstanding (Options)			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (in Thousands)
Options
Outstanding at December 26, 2015		1,051,867		$	14.60		2.46	$	1,916
Exercised		(5,846	)	$	13.74
Cancelled		(137,633	)	$	16.26
Outstanding at March 26, 2016		908,388		$	14.36		2.60	$	1,269
Exercisable at March 26, 2016		799,365		$	14.09		2.34	$	1,265

The aggregate intrinsic value in the above table represents the total pretax intrinsic value, based on the Company’s closing stock price of $14.13 as of March 24, 2016, the last trading day of the quarter, which would have been received by the option holders had all option holders exercised their options as of that date. The total intrinsic value of options exercised during the three months ended March 26, 2016 and March 28, 2015 was $3,000 and $0.8 million, respectively.

Restricted Stock Units (“RSUs”)

Time-based RSUs are valued using the market value of the Company’s common stock on the date of grant, assuming no expectation of dividends paid.

A summary of activity for RSUs is as follows:

Summary of activity for RSUs	Number of RSUs			Weighted Average Fair Value
Outstanding RSUs as of December 26, 2015		713,243		$	15.99
Granted		137,718		$	13.29
Released		(108,305	)	$	17.13
Cancelled		(14,348	)	$	15.48
Outstanding RSUs as of March 26, 2016		728,308		$	15.32

Market-Based Performance Stock Units (“PSUs”)

In addition to granting RSUs that vest on the passage of time only, the Company granted PSUs to an executive. The PSUs will vest in three equal tranches over one, two and three years based on the relative performance of the Company’s stock during those periods, compared to a peer group over the same period. If target stock price performance is achieved, 66.7% of the shares of the Company’s common stock subject to the PSUs will vest, and up to a maximum of 100% of the shares subject to the PSUs will vest if the maximum stock price performance is achieved for each tranche.

A summary of activity for PSUs is as follows:

Summary of activity for PSUs	Number of PSUs			Weighted Average Fair Value
Outstanding PSUs as of December 26, 2015		60,000		$	18.35
Granted		67,500		$	12.78
Released		(13,333	)	$	18.04
Cancelled		(6,667	)	$	18.04
Outstanding PSUs as of March 26, 2016		107,500		$	14.91

The preceding table reflects the maximum awards that can be achieved upon full vesting.

Valuation of PSUs

On the date of grant, the Company estimated the fair value of PSUs using a Monte Carlo simulation model. The assumptions for the valuation of PSUs are summarized as follows:

	2016 Award		2015 Award
Grant Date Fair Value Per Share	$	12.78	$	18.35
Weighted-average assumptions/inputs:
Expected Dividend		—		—
Range of risk-free interest rates		0.92%	0.25%-1.1%
Range of expected volatilities for peer group	22%-93%		23%-65%

Stock-based Compensation Expense

Stock-based compensation expense for all share-based payment awards made to the Company’s employees and directors pursuant to the employee stock option and employee stock purchase plans by function were as follows (in thousands):

	March 26, 2016		March 28, 2015
Cost of products	$	67	$	73
Cost of service		104		46
Research and development		285		280
Selling		492		500
General and administrative		741		672
Total stock-based compensation expense related to employee stock options and employee stock purchases	$	1,689	$	1,571