Major Customers and Concentrations of Credit Risk

We provide proprietary products and services to the Department of Defense and various United States Government agencies, and most of the aerospace and aircraft manufacturers who receive contracts directly from the U.S. Government as an original equipment manufacturer (“Primes”). In addition, we also service technology-driven markets in the industrial, medical and other end-use markets. As a result, we have significant net revenues from certain customers. Accounts receivable were diversified over a number of different commercial, military and space programs and were made by both operating segments. Net revenues from our top ten customers, including The Boeing Company (“Boeing”), Lockheed Martin Corporation (“Lockheed Martin”), Raytheon Company (“Raytheon”), Spirit AeroSystems Holdings, Inc. (“Spirit”), and United Technologies Corporation (“United Technologies”), represented the following percentages of total net sales:



	Years Ended December 31,
	2018		2017		2016
Boeing	17.0	%	16.3	%	17.3	%
Lockheed Martin	4.4	%	5.5	%	5.6	%
Raytheon	11.7	%	13.5	%	8.4	%
Spirit	9.5	%	8.2	%	8.2	%
United Technologies	4.6	%	4.7	%	5.3	%
Top ten customers⁽¹⁾	62.9	%	62.5	%	58.7	%

(1) Includes Boeing, Lockheed Martin, Raytheon, Spirit, and United Technologies.

Boeing, Lockheed Martin, Raytheon, Spirit, and United Technologies represented the following percentages of total accounts receivable:



	December 31,
	2018		2017
Boeing	8.0	%	7.8	%
Lockheed Martin	2.5	%	5.9	%
Raytheon	3.2	%	1.4	%
Spirit	—	%	13.5	%
United Technologies	2.5	%	2.3	%

In 2018, 2017 and 2016, net revenues from foreign customers based on the location of the customer were $71.9 million, $57.2 million and $56.4 million, respectively. No net revenues from a foreign country were greater than 3.0% of total net revenues in 2018, 2017, and 2016. We have manufacturing facilities in Thailand and Mexico. Our net revenues, profitability and identifiable long-lived assets attributable to foreign revenues activity were not material compared to our net revenues, profitability and identifiable long-lived assets attributable to our domestic operations during 2018, 2017, and 2016. We are not subject to any significant foreign currency risks as all our sales are made in United States dollars.