We have no finance lease obligations. Debt is summarized in the following table (in thousands):

	December 31,
	2020			2019
2011 Senior Notes	$	150,000		$	150,000
Credit Facility		111,000			157,000
Total long-term debt		261,000			307,000
Less: Debt issuance costs		(1,567	)		(1,717	)
Long-term debt, net	$	259,433		$	305,283

We have two series of senior notes outstanding with an aggregate principal amount of $150 million ("2011 Senior Notes") issued in a private placement transaction. Series A consists of $75 million in aggregate principal amount of notes that bear interest at a fixed rate of 4.01% and are due in full on September 30, 2021. Series B consists of $75 million in aggregate principal amount of notes that bear interest at a fixed rate of 4.11% and are due in full on September 30, 2023. Interest on each series of the 2011 Senior Notes is payable semi-annually on March 30 and September 30.

On June 22, 2020, we entered into Amendment No. 1 (the “Amendment”) to the Seventh Amended and Restated Credit Agreement, dated June 19, 2018 (as amended, the “Credit Facility”). The Amendment increases the maximum leverage ratio permitted under the Credit Facility for certain periods. Pursuant to the terms of the Amendment, the maximum leverage ratio permitted under the Credit Facility is as follows:

Quarter ending	Maximum leverage ratio permitted
June 30, 2020 up to and including June 30, 2021		3.00
September 30, 2021		2.75
December 31, 2021 and thereafter		2.50

Moreover, the Amendment modified the range of variable interest rates that the Credit Facility may bear to be a range from LIBOR plus 1.500% to LIBOR plus 2.875% and included the addition of a LIBOR floor of 0.50%. The Amendment also reduced the aggregate borrowing commitment under the Credit Facility to $225 million and the amount by which we may elect to increase the facility size, known as the “accordion” feature, to $50 million, subject to the satisfaction of certain conditions. Interest payment terms are variable depending upon the specific type of borrowing under this facility.

Any outstanding balance under the Credit Facility is due on maturity on June 19, 2023. Our available capacity at any point in time is reduced by outstanding borrowings and outstanding letters of credit which totaled $12.9 million, resulting in an available borrowing capacity under the Credit Facility of $101.1 million, at December 31, 2020. In addition to indebtedness under the Credit Facility, we had $6.1 million of outstanding letters of credit and performance guarantees and bonds from other sources as of December 31, 2020.

The Credit Facility remains unsecured, and contains customary representations, warranties, terms and conditions for similar types of facilities. The terms of the Credit Facility and 2011 Senior Notes require us to meet certain covenants, including, but not limited to, an interest coverage ratio (calculated as consolidated EBITDA divided by interest expense) and a leverage ratio (calculated as consolidated net indebtedness divided by consolidated EBITDA), where consolidated EBITDA (as defined in each agreement) and interest expense are calculated using the most recent four fiscal quarters. The Credit Facility and 2011 Senior Notes each include a cross-default provision, whereby a default under one agreement may trigger a default in the other agreement. The Credit Facility has the more restrictive covenants with a minimum interest coverage ratio of 3.0 to 1.0 and permits a maximum leverage ratio as described above. The Credit Facility allows non-cash charges such as impairment of assets, stock compensation and other non-cash charges to be added back in the calculation of consolidated EBITDA. The terms of our Credit Facility also allow us to negotiate in good faith to amend any ratio or requirement to preserve the original intent of the agreement if any change in accounting principles would affect the computation of any financial ratio or covenant of the Credit Facility. In accordance with the terms of the Credit Facility, our leverage ratio is 2.82, and our interest coverage ratio is 6.09, each for the period ended December 31, 2020. We believe that we are in compliance with all covenants contained in our Credit Facility and 2011 Senior Notes. We, along with certain of our material, wholly-owned subsidiaries are guarantors or co-borrowers under the Credit Facility and 2011 Senior Notes.

We entered into two interest rate swap agreements for a total of $50 million, including one of which was entered during the year ended December 31, 2020. See Note 15 - Derivative Instruments and Hedging Activities for additional information of our derivative instruments.

The estimated fair value of total debt at December 31, 2020 and 2019 approximated the book value of total debt. The fair value was estimated using Level 2 inputs by calculating the sum of the discounted future interest and principal payments through the maturity date.

During the year ended December 31, 2020, the Company incurred approximately $1.6 million in professional service fees and expenses associated with the evaluation of various corporate debt issuances and debt refinancing opportunities. These corporate finance and capital structure costs were expensed immediately and classified as interest expense. On October 16, 2020, we, along with our wholly-owned subsidiary Core Laboratories (U.S.) Interests Holdings, Inc. as issuer, entered into an agreement (the “2020 Notes Purchase Agreement”) to issue two new series of senior notes with aggregate principal amount of $60 million in a private placement transaction (“2020 Senior Notes”). The 2020 Senior Notes were issued and funded on January 12, 2021, and the proceeds were used to reduce outstanding borrowings under the Credit Facility. Series A of the 2020 Senior Notes consists of $45 million in aggregate principal amount that bear interest at a fixed rate of 4.09% and are due in full on January 12, 2026. Series B of the 2020 Senior Notes consists of $15 million in aggregate principal amount that bear interest at a fixed rate of 4.38% and are due in full on January 12, 2028. Interest on each series of the 2020 Senior Notes is payable semi-annually on June 30 and December 30, commencing on June 30, 2021.

The terms of the 2020 Senior Notes require us to meet certain covenants, including, but not limited to, an interest coverage ratio (calculated as consolidated EBITDA divided by interest expense) and a leverage ratio (calculated as consolidated net indebtedness divided by consolidated EBITDA), where consolidated EBITDA (as defined in the 2020 Note Purchase Agreement) and interest expense are calculated using the most recent four fiscal quarters; and a priority indebtedness ratio (calculated as Priority Indebtedness divided by Consolidated Total Assets (as defined in the 2020 Notes Purchase Agreement). The financial covenants for the 2020 Senior Notes are aligned with the Credit Facility and the associated 2020 Note Purchase Agreement also allows renegotiation of the ratios in consideration of changes in accounting principles. We, along with certain of our material, wholly-owned subsidiaries, are guarantors or co-borrowers under the 2020 Senior Notes. The proceeds of the 2020 Senior Notes were used to reduce outstanding borrowings under the Credit Facility, and along with $15 million of existing available capacity under the Credit Facility, will refinance the $75 million Series A 2011 Senior Notes due in September 2021. Accordingly, we have reclassified amounts due under the Series A 2011 Senior Notes as long-term debt.