Condensed Consolidated Satements of Income - USD ($)	3 Months Ended		6 Months Ended
	Nov. 30, 2017	Nov. 30, 2016	Nov. 30, 2017	Nov. 30, 2016
Income Statement [Abstract]
Sales, net	$ 4,811,774	$ 7,807,465	$ 11,379,494	$ 13,563,178
Cost of goods sold	3,550,083	5,061,495	8,500,151	9,369,084
Gross profit	1,261,691	2,745,970	2,879,343	4,194,094
Selling, general and administrative expenses	1,226,607	1,373,726	2,434,175	2,555,700
Operating income	35,084	1,372,244	445,168	1,638,394
Other income,  net	7,063	26,036	10,726	35,720
Income before provision for income taxes	42,147	1,398,280	455,894	1,674,114
Provision for income taxes (benefit)	(10,000)	460,000	102,000	526,000
Net income	$ 52,147	$ 938,280	$ 353,894	$ 1,148,114
Basic and diluted earnings per common share	$ 0.02	$ 0.27	$ 0.10	$ 0.34