13.Concentrations of Risk

The Company’s revenues are concentrated in a small group of customers with some individually having more than 10% of total revenues. Revenues from four customers that exceeded 10% of total revenues for the year ended December 31, 2019 were 38%,  17%,  13% and 10%. Accounts receivable from these same four customers were 0%,  13%,  0% and 34% of the total accounts receivable as of December 31, 2019. For the year ended December 31, 2018, two customers exceeded 10% of revenues and were 63% and 14% of total revenues. Accounts receivable from these same two customers were 0% and 0% of the total accounts receivable as of December 31, 2018.

Our customer revenue decreased from the year ended December 31, 2018 to December 31, 2019 by $1.5 million, which was driven by the loss of a key customer, which had over $1 million in sales in the year ended December 31, 2018.

The Company’s financial instruments that are exposed to concentrations of credit risk consist primarily of cash. Cash balances are maintained principally at major U.S. financial institutions and are insured by the Federal Deposit Insurance Corporation (“FDIC”) up to regulatory limits. From time to time, cash balances may exceed the FDIC insurance limit. The Company has not experienced any credit losses associated with its cash balances in the past.