CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Feb. 27, 2022	Feb. 28, 2021	Feb. 27, 2022	Feb. 28, 2021
Income Statement [Abstract]
Product sales	$ 53,074	$ 44,690	$ 138,158	$ 126,629
Cost of product sales	39,179	30,249	99,113	90,739
Gross profit	13,895	14,441	39,045	35,890
Operating costs and expenses:
Research and development	2,056	1,843	5,785	5,523
Selling, general and administrative	9,725	8,134	27,207	27,968
Legal settlement charge	0	0	0	1,763
Restructuring costs	5,865	2,023	8,406	2,826
Total operating costs and expenses	17,646	12,000	41,398	38,080
Operating loss	(3,751)	2,441	(2,353)	(2,190)
Interest income	20	13	66	31
Interest expense	(4,105)	(2,939)	(13,877)	(6,609)
Loss on debt refinancing	0	(1,110)	0	(1,110)
Other income (expense), net	454	72	642	64
Net loss before tax	(7,382)	(1,523)	(15,522)	(9,814)
Income tax benefit	276	58	5,012	1,025
Net loss from continuing operations	(7,106)	(1,465)	(10,510)	(8,789)
Loss from discontinued operations, net of tax	(5,744)	(4,033)	(50,258)	(21,010)
Net loss	$ (12,850)	$ (5,498)	$ (60,768)	$ (29,799)
Net loss per common share:
Net loss per common share - basic (in dollars per share)	$ (0.24)	$ (0.05)	$ (0.36)	$ (0.30)
Loss from discontinued operations- basic (in dollars per share)	(0.19)	(0.14)	(1.71)	(0.72)
Loss from discontinued operations- diluted (in dollars per share)	(0.19)	(0.14)	(1.71)	(0.72)
Net loss per common share - diluted (in dollars per share)	(0.43)	(0.19)	(2.07)	(1.02)
Diluted net loss per share:
Loss from continuing operations - diluted (in dollars per share)	(0.24)	(0.05)	(0.36)	(0.30)
Loss from discontinued operations- diluted (in dollars per share)	(0.19)	(0.14)	(1.71)	(0.72)
Total diluted net loss per share (in dollars per share)	$ (0.43)	$ (0.19)	$ (2.07)	$ (1.02)
Shares used in per share computation:
Basic (in shares)	29,482	29,323	29,459	29,282
Diluted (in shares)	29,482	29,323	29,459	29,282
Other comprehensive income (loss), net of tax:
Net unrealized gain (losses) on interest rate swaps (net of tax effect of $(101), $(99), $(291), and $(327))	$ 104	$ 387	$ 646	$ 1,092
Other comprehensive income, net	104	387	646	1,092
Total comprehensive loss	$ (12,746)	$ (5,111)	$ (60,122)	$ (28,707)
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]	Product [Member]	Product [Member]	Product [Member]	Product [Member]
Cost, Product and Service [Extensible Enumeration]	Product [Member]	Product [Member]	Product [Member]	Product [Member]