Here is the thread I use for basting quilts. It is crochet cotton and looking at the label on the inside of the cone it says it is size 20. I don't remember what I used this thread for originally but it works great for basting. At one time I did do crocheting but nothing too complicated but did make my oldest daughter a pink and white crocheted dress when she was about 9 months old. That was about 35 years ago though...time flies you know.
I dug it out when looking for some type of heavier thread for basting years ago. I have been using it for years and there is still a lot left on the cone. Look at the label, it had 1600 yards to begin with and I am thinking maybe I never used it for crocheting.