Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($)
 12 Months Ended
May 31, 2018
May 31, 2017
May 31, 2016
Income Statement [Abstract]      
Net sales $ 13,888,063 $ 12,397,643 $ 11,685,353
Cost of sales 7,822,749 7,511,836 6,818,058
Gross profit 6,065,314 4,885,807 4,867,295
Operating expenses:      
General, administration and sales 5,582,625 5,618,327 6,016,097
Research and development 327,317 256,164 287,672
Total operating expenses 5,909,942 5,874,491 6,303,769
Operating income (loss) 155,372 (988,684) (1,436,474)
Other income (expense), net 81,182 (56,671) (58,713)
Income (loss) before income taxes 236,554 (1,045,355) (1,495,187)
Provision for income taxes 25,915 28,009 20,002
Net income (loss) $ 210,639 $ (1,073,364) $ (1,515,189)
Net income (loss) per common share, basic      
Weighted average number of common shares, basic 3,422,724 2,995,910 2,995,910
Net income (loss) per common share, diluted $ 0.06 $ (0.36) $ (0.51)
Weighted average number of common shares, diluted 3,460,339 2,995,910 2,995,910
Comprehensive income (loss)      
Net income (loss) $ 210,639 $ (1,073,364) $ (1,515,189)
Foreign currency translation adjustment (108,735) (33,054) (27,573)
Total comprehensive income (loss) $ 101,904 $ (1,106,418) $ (1,542,762)