expression, noun-modifying (irregular)
good-quality; superior in quality
Prenominal phrase meaning 'of good quality'; used before nouns to describe high-quality items or materials.
See also: 質が良い
この店は質の良い家具を売っている。
This store sells good-quality furniture.
質の良い睡眠をとることが大切だ。
It's important to get good-quality sleep.
質が良い is a full clause meaning 'the quality is good', while 質の良い is a prenominal modifier meaning 'good-quality'.
Phrase composed of 質 (quality) + の (possessive particle) + 良い (good).