Note 12 - Credit Risk and Concentrations

Financial instruments that subject the Company to credit risk consist principally of trade accounts receivable and cash and cash equivalents. The Company performs certain credit evaluation procedures and does not require collateral for financial instruments subject to credit risk. The Company believes that credit risk is limited because the Company routinely assesses the financial strength of its customers and, based upon factors surrounding the credit risk of its customers, establishes an allowance for uncollectible accounts and, as a consequence, believes that its accounts receivable credit risk exposure beyond such allowances is limited.

The Company maintains cash deposits with financial institutions, which, from time to time, may exceed federally insured limits. Cash is also maintained at foreign financial institutions for its Canadian subsidiary and its majority-owned Saudi Arabia subsidiary. Cash in foreign financial institutions as of March 31, 2017 and December 31, 2016 was immaterial. The Company has not experienced any losses and believes it is not exposed to any significant credit risk from cash.

The following table sets forth the percentages of revenue derived by the Company from those customers which accounted for at least 10% of revenues during the three months ended March 31, 2017 and 2016 (in thousands):

As of March 31, 2017, Customer D represented approximately 12% of total accounts receivable. As of March 31, 2016, Customer C represented approximately 33% and Customer A represented approximately 17% of total accounts receivable.

As of March 31, 2017, one vendor represented approximately 38% of total gross accounts payable. Purchases from this vendor during the three months ended March 31, 2017 were $1.0 million. As of March 31, 2016, two vendors represented approximately 38% and 10% of total gross accounts payable. Purchases from these vendors during the three months ended March 31, 2016 were $4.5 million and $0.9 million.

For the three months ended March 31, 2017, three vendors represented approximately 16%, 12%, and 10% of total purchases. For the three months ended March 31, 2016, three vendors represented approximately 55%, 11% and 10% of total purchases.