Note 9 - Product Warranty - Changes in Product Warranty Liability (Details) - USD ($)	3 Months Ended	6 Months Ended
May 31, 2021	May 31, 2020	May 31, 2021	May 31, 2020
Balance, beginning	$ 295,581	$ 239,233	$ 291,454	$ 203,185
Settlements / adjustments	(72,888)	(37,146)	(102,267)	(65,722)
Warranties issued	44,807	66,146	78,313	130,770
Balance, ending	$ 267,500	$ 268,233	$ 267,500	$ 268,233

Amount as of the balance sheet date of the aggregate standard product warranty liability. Does not include the balance for the extended product warranty liability.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (c)(1),(c)(5)
-URI http://asc.fasb.org/extlink&oid=123368208&loc=d3e12565-110249

Name:	us-gaap_StandardProductWarrantyAccrual
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant