GEOGRAPHIC INFORMATION (Details) - Financial information about foreign and domestic operations and export sales - USD ($)	3 Months Ended		9 Months Ended
	Feb. 28, 2021	Feb. 29, 2020	Feb. 28, 2021	Feb. 29, 2020
GEOGRAPHIC INFORMATION (Details) - Financial information about foreign and domestic operations and export sales [Line Items]
Net Sales	$ 3,628,638	$ 1,176,889	$ 6,144,970	$ 3,967,712
UNITED STATES
GEOGRAPHIC INFORMATION (Details) - Financial information about foreign and domestic operations and export sales [Line Items]
Net Sales	133,000	165,000	374,000	389,000
Asia [Member]
GEOGRAPHIC INFORMATION (Details) - Financial information about foreign and domestic operations and export sales [Line Items]
Net Sales	756,000	404,000	1,653,000	1,863,000
Europe [Member]
GEOGRAPHIC INFORMATION (Details) - Financial information about foreign and domestic operations and export sales [Line Items]
Net Sales	2,611,000	509,000	3,781,000	1,226,000
South America [Member]
GEOGRAPHIC INFORMATION (Details) - Financial information about foreign and domestic operations and export sales [Line Items]
Net Sales	64,000	95,000	146,000	166,000
Middle East [Member]
GEOGRAPHIC INFORMATION (Details) - Financial information about foreign and domestic operations and export sales [Line Items]
Net Sales	65,000	4,000	190,000	313,000
Other [Member]
GEOGRAPHIC INFORMATION (Details) - Financial information about foreign and domestic operations and export sales [Line Items]
Net Sales			$ 1,000	$ 11,000