(12)   Concentration of Credit Risk

The following represents customers that accounted for 10% or more of total revenue during the years ended December 31, 2019, 2018, and 2017, and customers that accounted for 10% or more of total trade accounts receivable at December 31, 2019 and 2018:

During the years ended December 31, 2019 and 2018, all of the Company’s products were manufactured in our Scottsdale, Arizona facilities and by two vendors in China. During the year ended December 31, 2017, all the Company’s products were manufactured in Shullsburg, Wisconsin and Scottsdale, Arizona facilities and by two vendors in China. The Shullsburg, Wisconsin facility was closed in July 2017.