You're watching a commercial for a frozen pizza. The announcer on the commercial says this.
We use only the finest ingredients.
In advertisements, companies sometimes brag about having very high standards. To do this, they use the phrase "only the ___":
We use only the highest quality water in our beer.
We hire only the best and brightest engineers.
This phrase suggests that the company doesn't allow anything lower than this standard.
People don't use this phrase very often outside of advertisements.
Ingredients in cooking can be described as "high-quality":
The secret to good cooking is to start with fresh, high-quality ingredients.
But "the finest ingredients" sounds fancier and even more high-quality. You hear this phrase sometimese in advertisements.
Other things that can be described as "fine" include:
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