Operator
Good day. And welcome to the NuVasive Inc. Fourth Quarter and Full Year 2020 Earnings Conference Call. [Operator Instructions] As a reminder, this conference is being recorded. I would now like to turn the conference over to your host, Matt Harbaugh, Executive Vice President and Chief Financial Officer. Thank you. You may begin.
Matt Harbaugh --
Executive Vice President and Chief Financial Officer
Thank you. Welcome to NuVasive's Fourth Quarter and Full Year 2020 Earnings Call. The company's earnings release, which we issued earlier this afternoon, has been filed on Form 8-K with the Securities and Exchange Commission. We have also posted supplemental financial information and an overview on the acquisition of Simplify Medical we announced yesterday on our website in the Investor Relations section to accompany our discussion today. Joining me on the call is NuVasive' S CEO, Chris Barry. Chris will provide opening remarks and then I will share additional details on our financial results, before we open it up for Q&A. I would like to remind you that discussions during today's call will include forward-looking statements, which are based on current expectations and involve risks and uncertainties, assumptions and other factors, which, if they do not materialize or prove to be correct, could cause NuVasive's results to differ materially from those expressed or implied by such forward-looking statements. In particular, there is significant uncertainty around the duration and the impact of COVID-19 pandemic on the company's business, operations and financials. The COVID-19 pandemic continues to evolve, and it is important to note that our commentary reflects our best estimates as of today. Risks and uncertainties related to Simplify Medical and additional risks and uncertainties that may affect future results are described in our recent news releases and in other releases, and periodic filings with the Securities and Exchange Commission. NuVasive assumes no obligation to update any forward-looking statements or information, which speak as of their respective dates. This call will also include a discussion of several financial measures that are not calculated in accordance with generally accepted accounting principles or GAAP. We generally refer to these as non-GAAP financial measures. Many of the financial measures covered in today's call are on non-GAAP basis unless noted otherwise. These measures include non-GAAP gross margin, selling, general and administrative expenses, research and development expenses, operating margin, other income, and expense, tax expense, net income, diluted earnings per share, free cash flow and net sales reported on a constant currency basis. Reconciliations to the most directly comparable GAAP financial measures may be found in today's earnings release and the supplemental financial information, which are accessible on our website in the Investor Relations section. With that, I would like to turn the call over to Chris.