TSLX is a specialty finance company focused on lending to middle-market companies. Since TSLX began its investment activities in July 2011 through December 31, 2017, it has originated more than $7.3 billion aggregate principal amount of investments and retained approximately $4.4 billion aggregate principal amount of these investments on its balance sheet prior to any subsequent exits and repayments. TSLX seeks to generate current income primarily in U.S.-domiciled middle-market companies through direct originations of senior secured loans and, to a lesser extent, originations of mezzanine and unsecured loans and investments in corporate bonds and equity securities. The companies in which TSLX invests use capital to support organic growth, acquisitions, market or product expansion and recapitalizations. 100% of debt investments bore interest at floating-rates (when including investment specific hedges), which TSLX believes helps act as a portfolio-wide hedge against inflation. As of December 31, 2017, TSLX's portfolio had a fair value of approximately $1,693.7 million invested across 45 portfolio companies.
TSLX has elected to be regulated as a business development company, or a BDC, under the Investment Company Act of 1940 and the rules and regulations promulgated thereunder. TSLX is externally managed by TSL Advisers, LLC (the "Adviser"), a SEC-registered investment adviser with offices throughout the United States. The Adviser sources and manages TSLX's portfolio through a dedicated team of investment professionals with significant expertise in middle market lending. TSLX leverages the deep investment, sector, and operating resources of TPG Sixth Street Partners ("TSSP"), the dedicated special situations and credit platform of TPG, with approximately $20 billion of assets under management as of September 30, 2017, and the broader TPG platform, a leading global private investment firm with over $79 billion of assets under management as of September 30, 2017. TSLX is traded on the New York Stock Exchange under the ticker symbol "TSLX".