First Rate
First Class, Top Notch, Top Grade
noun, の adjective
This is a weird one. You have one stream. This is first rate stream material we have here, though. If you think about it, if you only have one stream (instead of a ton of streams), you can put all your effort and energy into it. When you do that, you're making sure it is a first rate stream in terms of quality and anything else.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
さすが、一流のピアニストは違うね。
That's something only first-rate pianists can do.
わたしの妹は、お金持ちで一流のしんしとこいに落ちました。
My sister fell in love with a wealthy, first-class gentleman.
これでコウイチは一流社会の仲間入りだ。たくさんのセレブに会ったり、シャンパンパーティにもすぐ行き始めるだろう。
Koichi is now a member of the upper class. He will meet a bunch of celebrities and start going to champagne parties soon.