5. Additional Paid-in Capital

Warrants

Warrant activity is summarized in the following table:


		Weighted		Weighted
		average		average
	Warrants	exercise price		remaining life
	outstanding	per share		(yrs.)	Intrinsic value
As of December 31, 2014	15,219,802	$	5.00	0.8	$	—
As of June 30, 2015	15,219,802	$	5.00	0.3	$	—

The 15,219,802 warrants outstanding expire in October 2015. Warrants were excluded from weighted average diluted shares as the exercise price is greater than the average price per common share.

Stock-Based Compensation

Under our Stock Option Plan (the “Plan”) and our Long-Term Equity Incentive Plan (the “LTIP”), we may grant options and/or restricted stock units (“RSUs”) or restricted stock awards to our directors, officers, employees and consultants. The combined maximum number of shares in the capital of Vista (“Common Shares”) that may be reserved for issuance under the Plan and the LTIP is a variable number equal to 10% of the issued and outstanding Common Shares on a non-diluted basis. Options and RSUs under the Plan and LTIP, respectively, are granted from time to time at the discretion of the Board of Directors of the Company (“Board”), with vesting periods and other terms as determined by the Board. Stock-based compensation expense for the three and six months ended June 30, 2015 and 2014 is as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
	2015		2014		2015		2014
Stock options	$	2	$	19	$	4	$	123
Restricted stock units		237		315		463		625
	$	239	$	334	$	467	$	748

As of June 30, 2015, stock options and RSUs had unrecognized compensation expense of $24 and $464, respectively, which is expected to be recognized over a weighted average period of 3.50 and 1.26 years, respectively. Stock options were excluded from weighted average diluted shares as the exercise prices are greater than the average price per common share. RSUs were excluded from weighted average diluted shares as they are considered anti-dilutive.

Stock Options

A summary of options under the Plan as of June 30, 2015 is set forth in the following table:


		Weighted average		Weighted average	Aggregate
	Number of	exercise price		remaining	intrinsic
	options	per option		contractual term	value
Outstanding - December 31, 2014	2,257,500	$	1.60	3.02	$	—
Outstanding - June 30, 2015	2,257,500	$	1.60	2.52	$	—

Exercisable - June 30, 2015	2,011,250	$	1.75	2.41	$	—

A summary of our unvested stock options as of June 30, 2015 is set forth in the following table:


				Weighted
		Weighted		average
		average		remaining
		grant-date		amortization
	Number of	fair value		period
	options	per option		(Years)
Unvested - December 31, 2014	246,250	$	0.22	3.99
Unvested - June 30, 2015	246,250	$	0.22	3.50

Restricted Stock Units

The following table summarizes the RSUs under the LTIP as of June 30, 2015:


		Weighted average
	Number	grant-date fair
	of units	value per unit
Unvested - December 31, 2014	3,692,829	$	0.74
Unvested - June 30, 2015	3,692,829	$	0.74

A portion of the RSU awards vest on a fixed future date provided the recipient continues to be affiliated with Vista on that date. Other RSU awards vest subject to certain performance and market criteria, including the accomplishment of certain corporate objectives and the Company’s share price performance. The vesting period for RSUs is at least one year. The average forfeiture is approximately 29%, based on historical market conditions.