9. Stockholders’ Equity

Common Stock

In March 2017, the Company issued and sold an aggregate of 1,495,000 shares of common stock at a public offering price of $76.00 per share, less the underwriters’ discounts and commissions, pursuant to an underwritten public offering. The Company received approximately $106.3 million in net cash proceeds after deducting underwriting discounts and commissions of $6.8 million and other offering expenses of $0.5 million.

In the first quarter of 2018, the Company granted and issued 53,256 restricted stock units with a fair value of $5.3 million in connection with the Buyout Agreement, as discussed in Note “6. Intangible Assets” and Note “8. Commitments and Contingencies.” The Company recorded the $5.3 million fair value of the shares issued to additional-paid in capital on the condensed consolidated balance sheet upon the issuance of the awards, with the associated expense being amortized into cost of sales over the period in which the Company receives future economic benefit from the buyout.

Equity Incentive Plans

Stock Options

Activity of stock options under the Penumbra, Inc. 2005 Stock Plan, the Penumbra, Inc. 2011 Equity Incentive Plan and the Amended and Restated Penumbra, Inc. 2014 Equity Incentive Plan (collectively the “Plans”) during the three months ended March 31, 2018 is set forth below:



	Number of Shares		Weighted-Average Exercise Price
Balance at December 31, 2017	2,107,104		$	17.58
Exercised	(117,039	)	11.32
Canceled/Forfeited	(633	)	18.80
Balance at March 31, 2018	1,989,432		17.95

Restricted Stock and Restricted Stock Units

Activity of unvested restricted stock and restricted stock units under the Plans during the three months ended March 31, 2018 is set forth below:



	Number of Shares		Weighted -Average Grant Date Fair Value
Unvested at December 31, 2017	742,405		$	38.86
Granted	81,436		100.84
Vested	(168,772	)	48.12
Canceled/Forfeited	(1,000	)	84.65
Unvested at March 31, 2018	654,069		44.11

As of March 31, 2018, 641,209 restricted stock and restricted stock units are expected to vest.

Stock-based Compensation

The following table sets forth the stock-based compensation expense included in the Company’s condensed consolidated statements of operations and comprehensive income (loss) for the three months ended March 31, 2018 and 2017 (in thousands):



	Three Months Ended March 31,
	2018		2017
Cost of revenue	$	219	$	309
Research and development	368		253
Sales, general and administrative	3,567		3,450
Total	$	4,154	$	4,012

As of March 31, 2018, total unrecognized compensation cost was $27.6 million related to unvested share-based compensation arrangements which is expected to be recognized over a weighted average period of 2.3 years.

The total stock-based compensation cost capitalized in inventory was $0.3 million and $0.2 million as of March 31, 2018 and December 31, 2017, respectively.