Long-term debt balances and associated interest rates and maturities are as follows:


	March 31, 2022			December 31, 2021
Note payable with quarterly principal and interest payments of $30,917 per quarter, with fixed interest of 6.94% and maturity August 12, 2024.	$	260,307		$	286,255
Note payable with quarterly principal and interest payments of $30,917 per quarter, with fixed interest of 6.94% and maturity July 15, 2023.		174,733			202,142
Note payable with quarterly principal and interest payments of $56,548 per quarter, with fixed interest of 4.89% and maturity March 20, 2025.		627,556			675,836
Note payable with quarterly principal and interest payments of $8,250 per quarter, with fixed interest of 5.44% and maturity September 10, 2026.		394,362			413,574
		1,456,958			1,577,807
Less current maturities		(501,453	)		(494,173	)
Long-term debt	$	955,505		$	1,083,634

The notes payable were issued in connection with various equipment purchases. The notes are collateralized by the original purchased equipment which had an aggregate net book value of $1.8 million as of March 31, 2022.

On February 12, 2021, the Company entered into the 2021 Credit Agreement to refinance and replace the 2020 Credit Agreement, entered into on February 14, 2020.

On October 4, 2021, the Company repaid the $20.0 million of outstanding borrowings under the 2021 Credit Agreement, plus interest accrued and unpaid on the loan through the date of repayment. Upon repayment, the 2021 Credit Agreement was terminated. The Company incurred incremental fees related to the payoff totaling $7 thousand.

The 2021 Credit Agreement was guaranteed by two significant Company stockholders, Kirin and Mitsui. Each stockholder guaranteed 50% of the total amount of the loan, or $10 million.

Under the respective 2021 Fee Letters, the Company has agreed to reimburse Mitsui and/or Kirin in cash for any amounts that Mitsui and/or Kirin pays under its respective guarantee of the 2021 Credit Agreement. However, if the Company is unable to reimburse such amounts wholly or partially to Mitsui and/or Kirin, then the Company and Mitsui and/or Kirin may agree to deem such unreimbursed amounts to be made for the Company’s benefit in consideration for its debt or equity securities on terms reasonably satisfactory to Mitsui and/or Kirin and the Company.

The guarantee fee during the period of February 14, 2020 through February 13, 2021 was calculated as 2.00% of the outstanding borrowings under the Credit Agreements, to be paid by the borrower on an annual basis. Beginning February 12, 2021, the guarantee fee was calculated as 1.20% of the outstanding borrowings under the Credit Agreements. The Company recorded $99 thousand of related expense during the three months ended March 31, 2021, which are included in the guarantee fees in the condensed consolidated statements of operations. Upon repayment of the outstanding borrowings under the 2021 Credit Agreement, the related Kirin and Mitsui guarantees were released and terminated.

In 2018, an irrevocable standby letter of credit was issued by a bank on the Company’s behalf as required by the landlord of the South Carolina production facility, and guarantees were issued by related parties. The standby letter of credit was for $4.9 million and had an original expiration date of December 3, 2019, with automatic renewals until October 31, 2037. The standby letter of credit is guaranteed 50% by Kirin and Mitsui, to whom the Company pays an annual guarantee fee. Under the respective 2018 Fee Letters, the guarantee fee is based on the 12-month USD LIBOR rate, plus 3% on the amount of the guarantee. The letter of credit has an annual fee of $20 thousand.

On October 29, 2021, the Company deposited $4.9 million into a restricted interest-bearing account with SMBC to fund the standby letter of credit and release the guarantees provided by Kirin and Mitsui. The Company incurred total guarantee fee expense for the standby letter of credit for the three months ended March 31, 2021 of $40 thousand, which has been included in guarantee fees in the condensed consolidated statements of operations.