na-adjective, noun which may take the genitive case particle 'no', noun
good quality; high quality; fine quality
Describes something of inherently good or superior quality. Often used attributively (良質な/良質の) before nouns like 素材, サービス, 睡眠.
このレストランは良質な食材を使っている。
This restaurant uses high-quality ingredients.
良質の睡眠
Getting good-quality sleep is important for health.