What is the open and close cam mean?

Hello! I can't tell from your photos if you have an open cam or closed cam. It's easy enough to figure out, though; the open cam 15-195B is hollow straight through. If you hold it up to your eye, you can look right out to the other side. Meanwhile the closed cam 15-195 is solid at the back, so you can't see through it. That is the only difference between them.