The Amended and Restated Omnibus Equity Incentive Plan (“the Plan”) provides for various forms of stock-based incentives. To date, of the available forms of awards under the Plan, the Company has granted only stock options, restricted stock, unrestricted share grants, and restricted stock units (“RSUs”). Options under the Plan are granted at fair market value on the date of grant, become exercisable generally over a three-year period, or as determined by the Board of Directors, and expire over periods not exceeding 10 years from the date of grant. Certain option and share awards provide for accelerated vesting if there is a change in control and pre-established financial metrics are met (as defined in the Plan). Grants of restricted stock outstanding under the Plan generally vest over periods of one to three years. Grants of RSUs outstanding under the Plan generally vest based on service, performance, or a combination of both. On June 14, 2018, stockholders approved a proposal to increase the number of shares under the Plan by 2,235,000 shares, for a total of 15,385,000 shares. As of January 3, 2020, there were 1,633,221 shares available for grant under the Plan.

There was no net income tax benefit recognized in the Consolidated Statements of Operations for stock-based compensation expense for non-qualified stock options, as the Company fully offsets net deferred tax assets with a valuation allowance (see Note 10). The Company does not recognize deferred income taxes for incentive stock option compensation expense, and records a tax deduction only when a disqualified disposition has occurred (see Note 10).

The following table represents the fair value of stock-based compensation granted during the year ended 2019 (in thousands):

The cost that has been charged against income for stock-based compensation is set forth below (in thousands):

	Years Ended
	2019		2018		2017
Employee stock option	$	8,144	$	4,013	$	1,731
Restricted stock		320		274		186
Restricted stock units		1,905		2,120		1,226
Nonemployee stock options		178		355		18
Total stock-based compensation expense	$	10,547	$	6,762	$	3,161

The Company recorded stock-based compensation expense in the following categories (in thousands):

	Years Ended
	2019		2018		2017
Cost of sales	$	52	$	15	$	8
General and administrative		4,010		2,635		1,487
Marketing and selling		3,318		1,805		805
Research and development		3,167		2,307		861
Total stock-based compensation expense, net		10,547		6,762		3,161
Amounts capitalized as part of inventory		1,017		637		372
Total stock-based compensation expense, gross	$	11,564	$	7,399	$	3,533

As of January 3, 2020, total unrecognized compensation cost related to non-vested stock-based compensation arrangements granted under the Plan were as follows (in thousands):

This cost is expected to be recognized over a weighted-average period of approximately two years.

The fair value of each option award is estimated on the date of grant using a Black-Scholes option valuation model applying the weighted-average assumptions noted in the following table. Expected volatilities are based on historical volatility of the Company’s stock. The expected term of options granted is derived from the historical exercises and post-vesting cancellations, and represents the period of time that options granted are expected to be outstanding. The Company has calculated an 8% estimated forfeiture rate based on historical forfeiture experience. The risk-free rate is based on the U.S. Treasury yield curve corresponding to the expected term at the time of the grant.

	Years Ended
	2019			2018			2017
Expected dividend yield		0	%		0	%		0	%
Expected volatility		53	%		53	%		57	%
Risk-free interest rate		2.40	%		2.71	%		1.96	%
Expected term (in years)		5.66			5.72			5.67

A summary of option activity under the Plan for the year ended January 3, 2020 is presented below:

	Shares (in 000’s)			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (years)		Aggregate Intrinsic Value (in 000’s)
Outstanding at December 28, 2018		3,920		$	11.80
Granted		824			35.40
Exercised		(388	)		8.92
Forfeited or expired		(30	)		25.87
Outstanding at January 3, 2020		4,326		$	16.46		6.51	$	78,995
Exercisable at January 3, 2020		3,047		$	10.66		5.54	$	72,393

A summary of unvested options activity under the Plan for the year ended January 3, 2020 was as follows:

	Shares (in 000’s)			Weighted- Average Grant-Date Fair Value
Unvested at December 28, 2018		1,260		$	9.67
Granted		824			17.95
Forfeited or expired		(30	)		13.29
Vested		(775	)		8.83
Unvested at January 3, 2020		1,279		$	15.44

The weighted average grant date fair value of options granted and the total intrinsic value of options exercised were as follows:

	Years Ended
	2019		2018		2017
Weighted-average grant-date fair value	$	17.95	$	11.95	$	5.42
Intrinsic value of options (in thousands)	$	9,955	$	13,699	$	3,065

A summary of restricted stock activity under the Plan for the year ended January 3, 2020 was as follows:

	Shares (in 000’s)			Weighted- Average Grant- Date Fair Value
Outstanding at December 28, 2018		11		$	29.80
Granted		11			29.39
Vested		(11	)		29.80
Outstanding at January 3, 2020		11		$	29.39

A summary of restricted stock units’ activity under the Plan for the year ended January 3, 2020 was as follows:

	Units (in 000’s)			Weighted- Average Grant- Date Fair Value
Outstanding at December 28, 2018		322		$	10.46
Granted		19			37.98
Vested		(229	)		12.58
Forfeited or expired		(8	)		11.57
Outstanding at January 3, 2020		104		$	10.79

On August 10, 2018, the Company closed an offering of its common stock. As part of this transaction, the Company issued 1,999,850 shares of its common stock at a price of $36.309 per share. Net proceeds, after deducting expenses, received from this offering were $72,150,000.