10.    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 two customers that exceeded 10% of total revenues for the three months ended March 31, 2020 were 53% and 32%.  Accounts receivable from these same four customers were 26%, and 18% of the total accounts receivable as of March 31, 2020.  For the three months ended March 31, 2019, three customers exceeded 10% of revenues and were 70%,  14%  and 11% of total revenues.  Accounts receivable from these same two customers were 33% and 13% of the total accounts receivable as of December 31, 2019.

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.