Note 1 - Summary of Significant Accounting Policies (Details Textual)	12 Months Ended
Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)
Accounts Receivable, Allowance for Credit Loss, Current	$ 39,000	$ 59,000
Inventory Valuation Reserves, Ending Balance	86,000	45,000
OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax	$ 0	$ 0	$ 0
Supplier Concentration Risk [Member] \| Cost of Goods and Service Benchmark [Member]
Number of Suppliers	5	3
Concentration Risk, Percentage	80.00%	60.00%
Building [Member]
Property, Plant and Equipment, Useful Life (Year)	30 years
Furniture, Fixtures, Equipment and Computer Software [Member] \| Minimum [Member]
Property, Plant and Equipment, Useful Life (Year)	3 years
Furniture, Fixtures, Equipment and Computer Software [Member] \| Maximum [Member]
Property, Plant and Equipment, Useful Life (Year)	10 years

Represents the number of major suppliers of the Company.

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- Definition

Amount of allowance for credit loss on accounts receivable, classified as current.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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- Definition

Amount of valuation reserve for inventory.

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Amount, after tax and before adjustment, of unrealized holding gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Excludes unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale.

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- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

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