Quarterly Financial Data (unaudited) - Summary of quarterly financial data (Details) - USD ($)	3 Months Ended								12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Quarterly Financial Data (unaudited)
Net sales	$ 8,511,000	$ 8,097,000	$ 7,310,000	$ 7,976,000	$ 7,690,000	$ 8,316,000	$ 8,107,000	$ 7,269,000	$ 31,894,262	$ 31,381,521	$ 33,759,953
Gross profit	1,378,000	1,586,000	1,347,000	1,260,000	1,405,000	1,550,000	1,205,000	879,000	5,570,616	5,038,627	6,450,442
Loss from operations	(638,000)	(305,000)	(1,512,000)	(607,000)	(433,000)	(353,000)	(762,000)	(1,226,000)	(3,062,179)	(2,774,022)	(1,995,614)
Net income (loss)	$ (539,000)	$ (330,000)	$ (1,531,000)	$ (614,000)	$ (474,000)	$ 378,000	$ (779,000)	$ (1,235,000)	$ (3,014,100)	$ (2,109,685)	$ (2,192,170)
Basic earnings (loss) per share	$ (0.14)	$ (0.08)	$ (0.38)	$ (0.15)	$ (0.12)	$ 0.09	$ (0.19)	$ (0.31)	$ (0.75)	$ (0.53)	$ (0.55)
Diluted earnings (loss) per share	$ (0.14)	$ (0.08)	$ (0.38)	$ (0.15)	$ (0.12)	$ 0.09	$ (0.19)	$ (0.31)	$ (0.75)	$ (0.53)	$ (0.55)