Note 9 - Commitments and Contingencies - Changes in Product Liability Included in Accrued Liabilities (Details) - USD ($)	6 Months Ended	12 Months Ended
	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2016
Beginning balance	$ 588,000	$ 566,000	$ 627,000
Warranties issued during the period	95,000	120,000	97,000
Settlements made during the period	(359,000)	(93,000)	(287,000)
Changes in liability for pre-existing warranties during the period	(33,000)	(5,000)	129,000
Ending balance	$ 291,000	$ 588,000	$ 566,000