The phrase ‘these ones’ is often considered informal or colloquial. In standard English, it’s more accurate to simply say ‘these’ when referring to multiple items.
The use of ‘ones’ after ‘these’ can lead to redundancy because ‘these’ already indicates a plural noun. For example, instead of saying, ‘I like these ones,’ it would be clearer and more grammatically correct to say, ‘I like these.’
However, in casual conversation, people often use phrases like ‘these ones’ for emphasis or clarity, especially when distinguishing between different groups of objects. While it’s not technically wrong, it’s best to avoid it in formal writing or situations where standard grammar is expected.