Sometimes "these ones" is OK, and sometimes the "ones" is redundant. Learn when.
The word "ones" can be plural, as in "I like the red ones." You could even say "I like these red ones." Imagine that "ones" is standing in for the word "roses" or apples." But "I like these ones" is redundant and incorrect. "These" is already standing in for the noun. You should say simply "I like these" instead.
The situation is the same with "those":
He likes those ones. (redundant)
He likes those. (better)
The phrases "this one" and "that one" don’t seem to bother linguists, but it doesn't hurt to take a second look when you use the phrases to make sure you aren't being unnecessarily wordy.
Get more tips like this in The Grammar Devotional: