Note 8 - Product Warranty - Changes in Product Warranty Liability (Details) - USD ($)	3 Months Ended	9 Months Ended
Aug. 31, 2018	Aug. 31, 2017	Aug. 31, 2018	Aug. 31, 2017
Balance, beginning	$ 71,216	$ 152,964	$ 68,452	$ 134,373
Settlements / adjustments	(73,108)	(46,469)	(214,674)	(155,603)
Warranties issued	73,155	26,699	217,485	154,424
Balance, ending	$ 71,263	$ 133,194	$ 71,263	$ 133,194

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