I heard this from someone the other day.

Problem:
The word “ones” is unnecessary in this phrase.

Explanation:
The individual said a sentence such as “Those ones are bigger.”

The word “those” in the phrase “Those ones …” is acting as a determiner.

Other examples of “those” as a determiner include:

• “I like those chocolates.”
• “Do you want those tickets?”
• “He should give her those flowers.”

Also, it is possible to pluralize the singular numerical pronoun “one”, as in the following examples:

• “I like the vanilla ones.”
• “The ones in green are tickets for the front row.”
• “Are the pink flowers the ones that he wants?”

However, when the word “ones” is preceded by a plural determiner (such as “those”), it is best to drop the word “ones”, thereby converting the determiner “these” into a demonstrative pronoun, as shown in the following examples:

• “I like those.”
• “Do you want those?”
• “He should give her those.”

Solution:
“Those …”