Effect of foreign-derived intangible income deductions Effect of foreign-derived intangible income deductions Expected volatility Maximum Unrealized gain (loss) from marketable securities Represents the monetary amount of Unrealized gain (loss) from marketable securities, during the indicated time period. Financial Instrument [Axis] Schedule of income taxes disaggregated by federal and state Schedule of Effective Income Tax Rate Reconciliation Stock-Based Compensation NOTE 11. STOCK REPURCHASE PROGRAM NOTE 1. BASIS OF PRESENTATION Accounts payable {1} Accounts payable Prepaid expenses and other assets {1} Prepaid expenses and other assets Cash dividends ($4.00 per share of common stock) Cash dividends ($4.00 per share of common stock) Comprehensive income Comprehensive income Total comprehensive income Cash dividends declared per common share Other income Selling, general, and administrative Research and development Product sales Marketable securities, long-term (amortized cost of $23,726,027 as of March 31, 2026, and $26,353,692 as of March 31, 2025) Details {1} Details BALANCE SHEETS - Parenthetical Amendment Flag Entity Small Business Share Repurchase Program, Authorized, Amount Reserve for obsolete inventory Represents the Reserve for obsolete inventory, during the indicated time period. Federal {2} Federal Federal {1} Federal Statistical Measurement Work in process Gross Unrealized Holding Losses {1} Gross Unrealized Holding Losses Fair Value, Inputs, Level 2 (1 Year Lease, Cost {1} Lease, Cost Fair Value of available-for-sale securities Fixed Assets Cash and Cash Equivalents NOTE 12. INFORMATION AS TO EMPLOYEE STOCK PURCHASE, SAVINGS, AND SIMILAR PLANS NOTE 6. INVENTORIES Supplemental disclosures of cash flow information Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation, Beginning Balance Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation, Beginning Balance Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation, Ending Balance Additional Paid-in Capital Net income Net income Marketable securities, short-term (amortized cost of $18,118,460 as of March 31, 2026, and $13,730,266 as of March 31, 2025) Registrant CIK Scenario Lessee, Operating Lease, Liability, Maturity Schedule of Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Grant Date Intrinsic Value Disclosure of Share-Based Compensation Arrangements by Share-Based Payment Award Accounts Receivable and Allowance for Credit Losses Details {5} Details Unrealized gain on marketable securities, net of tax Common Stock, Shares Authorized Accrued payroll and other Current liabilities Total current assets Total current assets Document Financial Statement Error Correction Phone Fax Number Description Entity Incorporation, State or Country Code Subsequent Event, Date 2032 Operating cash flows for leases Unrecognized Tax Benefits Section 174 R&D expense Represents the Section 174 R&D expense, during the indicated time period. Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross Total fair value of option grants Represents the monetary amount of Total fair value of option grants, during the indicated time period. Finished goods Available for Sale Securities, Estimated Fair Value Represents the monetary amount of Available for Sale Securities, Estimated Fair Value, as of the indicated date. Available for Sale Securities, Gross Unrealized Holding Losses Represents the monetary amount of Available for Sale Securities, Gross Unrealized Holding Losses, as of the indicated date. Schedule of Earnings Per Share, Basic and Diluted FINANCING ACTIVITIES Purchases of marketable securities Purchases of marketable securities Changes in operating assets and liabilities Income from operations Income from operations Common Stock, Shares, Outstanding Entity Public Float Document Period End Date Document Annual Report Defined Benefit Plan, Plan Assets, Contributions by Employer Customer A Represents the Customer A, during the indicated time period. 2028 Net Deferred Tax Assets/ (Liabilities) Net Deferred Tax Assets/ (Liabilities) State (Minnesota) {2} State (Minnesota) Options Outstanding, Aggregate Intrinsic Value Options Outstanding, Aggregate Intrinsic Value Investment Type [Axis] Schedule of Deferred Tax Assets and Liabilities Notes Accounts receivable Accounts receivable Income before income taxes Income before taxes Total shareholders' equity Total shareholders' equity Fixed assets Prepaid expenses and other assets ICFR Auditor Attestation Flag Entity Current Reporting Status Entity Voluntary Filers Entity Address, City or Town Scenario [Axis] Options Outstanding, Weighted Average Remaining Contractual Life (Years) Options Outstanding, Weighted Average Remaining Contractual Life (Years) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Available for Sale Securities, Amortized Cost Represents the monetary amount of Available for Sale Securities, Amortized Cost, as of the indicated date. Unrealized Gain (Loss) on Investments {1} Unrealized Gain (Loss) on Investments Available-for-Sale Securities Shares Outstanding, Starting Shares Outstanding, Starting Shares Outstanding, Ending Equity Components [Axis] Details {4} Details Weighted average shares outstanding Total liabilities and shareholders' equity Total liabilities and shareholders' equity Operating lease Less accumulated depreciation and amortization Entity Listing, Par Value Per Share Trading Symbol Fiscal Year End Total lease liabilities Depreciation and amortization Represents the Depreciation and amortization, during the indicated time period. Paid time off accrual Represents the Paid time off accrual, during the indicated time period. Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number Options Exercisable Expected life (years) Raw materials Estimated fair value of assets that were accounted for at fair value on a recurring basis Revenue Recognition Policies NOTE 13. SUBSEQUENT EVENT NOTE 10. CONCENTRATIONS Purchases of fixed assets Purchases of fixed assets Accrued payroll and other {1} Accrued payroll and other Adjustments to reconcile net income to net cash provided by operating activities Fixed assets, net Fixed assets, net Leasehold improvements Accounts receivable, net of allowance for credit losses of $15,000 Title of 12(b) Security Document Transition Report 2027 Operating lease {1} Operating lease Deferred Tax Assets Deferred Tax Assets Total {1} Total Tax credits (R&D and manufacturing credits) Tax credits (R&D and manufacturing credits) Minimum Income Taxes NOTE 4. NEW ACCOUNTING STANDARDS NOT YET ADOPTED NOTE 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Inventories Inventories Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period Total expenses Total expenses Expenses Accumulated other comprehensive loss LIABILITIES AND SHAREHOLDERS' EQUITY Deferred tax assets Auditor Firm ID Document Fiscal Year Focus Customer 2029 Other Unrecognized stock-based compensation Represents the monetary amount of Unrecognized stock-based compensation, during the indicated time period. Inventories {1} Inventories NOTE 8. INCOME TAXES Decrease in cash and cash equivalents Decrease in cash and cash equivalents Net cash used in financing activities Net cash used in financing activities Payment of dividends to shareholders Payment of dividends to shareholders Proceeds from maturities of marketable securities Non-cash operating lease expense (credit) Non-cash operating lease expense (credit) Deferred income taxes Shares Granted, Value, Share-Based Payment Arrangement, after Forfeiture Provision for income taxes Provision for income taxes Long-term operating lease liability Accounts payable Auditor Location City Area Code Share Repurchase Program, Remaining Authorized, Amount Customer [Axis] Operating lease cost State (Minnesota) {1} State (Minnesota) Unrealized gain on marketable securities, net of tax {1} Unrealized gain on marketable securities, net of tax Gross Unrealized Holding Losses {2} Gross Unrealized Holding Losses Corporate Bond Securities Fair Value, Inputs, Level 1 Available for Sale Securities, Debt Maturities after Three through Seven Years, Fair Value Represents the monetary amount of Available for Sale Securities, Debt Maturities after Three through Seven Years, Fair Value, as of the indicated date. Marketable securities NOTE 9. LEASES Net cash provided by operating activities Net cash provided by operating activities Retained Earnings Weighted Average Number of Shares Outstanding, Diluted Additional paid-in capital Entity Common Stock, Shares Outstanding Entity Address, State or Province Document Type Imputed lease interest Imputed lease interest 2031 Remaining lease term (months) Section 263A UNICAP inventory Represents the Section 263A UNICAP inventory, during the indicated time period. Non-deductible items Represents the monetary amount of Non-deductible items, during the indicated time period. Estimated Fair Value {2} Estimated Fair Value Marketable Securities, Accrued Interest Receivable Represents the monetary amount of Marketable Securities, Accrued Interest Receivable, as of the indicated date. Available for Sale Securities, Debt Maturities after One through Three Years, Fair Value Represents the monetary amount of Available for Sale Securities, Debt Maturities after One through Three Years, Fair Value, as of the indicated date. US Treasury Securities Schedule of Components of Income Tax Expense (Benefit) NOTE 5. MARKETABLE SECURITIES