When I got my new primary machine, I knew I wanted a "top loading bobbin" because I use a table and it is a pain to take off the acrylic panel and lift the machine and on and on. I got one but what it is, is just an opening to a standard bobbin with the little bobbin case.
What I really wanted was a "drop in" bobbin with the little window where I could see my bobbin before starting those long rows.
Maybe next time!