The expense relating to stock options is recognized on a straight-line basis over the requisite service period, usually the vesting period, based on the grant-date fair value. The unamortized compensation cost, as of June 30, 2020, was $0.2 million related to stock options and is expected to be recognized as expense over a weighted-average period of approximately 1.9 years. The expense related to restricted stock units (RSUs) is recognized over a three-to-five year vesting period and is based on the fair value of the underlying stock on the dates of grant. The unamortized compensation cost, as of June 30, 2020, was $0.2 million related to RSUs and is expected to be recognized as expense over a weighted-average period of approximately 1.6 years.

For the three and six months ended June 30, 2020 and 2019, there were no excess tax benefits associated with the exercise of stock options due to the Company’s historical loss positions.

There were no awards granted during the six months ended June 30, 2020. The fair value of the Company’s stock options granted during the six months ended June 30, 2019 was estimated on the grant dates using the Black-Scholes valuation option-pricing model with the following assumptions:

The risk-free interest rate was derived from the Daily Treasury Yield Curve Rates, as published by the U.S. Department of the Treasury as of the grant date for terms equal to the expected terms of the options. The expected volatility was based on the historical volatility of the Company’s stock price over the expected term of the options. The expected term of options granted was derived from historical data based on employee exercises and post‑vesting employment termination behavior. A dividend yield of zero is applied because the Company has never paid dividends and has no intention to pay dividends in the near future. The Company accounts for forfeitures as they occur.

In August 2019, the Company’s stockholders approved the 2019 Stock Incentive Plan (the 2019 Plan), and, as a result, the Amended and Restated 2010 Equity Incentive Plan (the 2010 Plan) was terminated. No future grants of awards will be made under the 2010 Plan, although it will continue to govern prior awards granted thereunder, until all such awards granted have been exercised, forfeited, canceled, expired or otherwise terminated in accordance with their terms. The 2019 Plan authorizes the board of directors or the compensation committee of the board of directors to grant a broad range of awards including stock options, stock appreciation rights, restricted stock, performance-based awards, and restricted stock units. Under the 2019 Plan, 182,500 shares have been reserved for issuance.

The term of all incentive stock options granted to a person who, at the time of grant, owns stock representing more than 10% of the voting power of all classes of the Company’s stock may not exceed five years. The exercise price of stock options granted under the 2019 Plan must be at least equal to the fair market value of the shares on the date of grant. Generally, options granted under the 2019 Plan will vest over a three to four-year period and have a term of 10 years from the date of grant. In addition, the 2019 Plan provides for automatic acceleration of vesting for options granted to non-employee directors upon a change of control of the Company.

A summary of option activity under the 2010 Plan and the 2019 Plan is presented below (in thousands, except exercise price):

			Options outstanding
					Weighted
	Shares				Average
	Available		Number of		Exercise
	for Grant		Shares		Prices
Balance as of January 1, 2020		88		161	$	10.85
Activity		—		—	$	—
Balance as of June 30, 2020		88		161	$	10.85

A summary of RSU activity under the Plan is presented below (in thousands, except for fair value):

				Weighted
				Average
	Number of			Grant-Date
	Shares			Fair Value
Non-vested shares as of January 1, 2020		103		$	3.75
Vested		(21	)	$	3.80
Non-vested shares as of March 31, 2020		82		$	3.74
Cancelled		(1	)	$	4.55
Non-vested shares as of June 30, 2020		81		$	3.73

The total intrinsic value of the RSUs outstanding as of June 30, 2020 was $0.1 million.

The following table summarizes significant ranges of outstanding and exercisable options as of June 30, 2020 (in thousands, except contractual life and exercise price):

	Options Outstanding						Options Exercisable
			Weighted
			Average
			Remaining		Weighted				Weighted
			Contractual		Average				Average		Aggregate
	Number		Life		Exercise		Number		Exercise		Intrinsic
Range of Exercise Price	Outstanding		(in Years)		Price		Exercisable		Price		value
$1.57 - $14.99		144		8.76	$	2.64		43	$	3.10	$	28
$15.00 - $25.59		8		3.24	$	15.00		5	$	15.00	$	—
$25.60 - $143.99		3		3.86	$	41.88		2	$	47.46	$	—
$144.00 - $409.99		5		6.15	$	144.00		5	$	144.00	$	—
$410.00 - $924.00		1		4.69	$	430.64		1	$	430.64	$	—
$1.57 - $924.00		161		8.29	$	10.85		56	$	25.97	$	28

There were no stock options exercised during the six months ended June 30, 2020 or 2019.