Note 9 - Product Warranty - Changes in Product Warranty Liability (Details) - USD ($)	3 Months Ended
Feb. 29, 2020	Feb. 28, 2019
Balance, beginning	$ 203,185	$ 96,785
Settlements / adjustments	(28,576)	(132,297)
Warranties issued	64,624	61,369
Balance, ending	$ 239,233	$ 25,857

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=68068213&loc=d3e12565-110249

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