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Note 8 - Significant Customers / Concentration / Disaggregated Revenue - Sales by Product Line (Details) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Net Sales $ 9,297,186 $ 3,598,028 $ 16,718,384 $ 5,989,410
Ceramic Diesel Particulate [Member]        
Net Sales 747,234 1,609,057 2,990,502 3,537,162
Liquid Filters [Member]        
Net Sales 8,453,136 1,988,971 13,493,469 2,452,248
Development Projects [Member]        
Net Sales $ 96,815 $ 234,413