THEY REALLY DO WORK AND REALLY ARE 4 OZ!!
At first when I received them They did not appear to be 4 oz size. They were smaller in diameter and height than my usual, more costly jars. But in filling a jar with 4 oz of water...yes, indeed, filled with 4 oz with a small amount of room left over. I really like these jars. One reviewer said they were hard to open. What I've discovered is that when they are squeezed too tightly when opening they ARE hard to open. So no need to struggle. Just use light pressure when opening. The inner security lid works great.  These are much more economical then where I have previously been buying 4 oz jars. And well made.
Rating: 5 stars