I picked up a closeup lense today, and I now notice the glass itself is loose within the ring. It's not coming out, and it moves only a little bit, I'm wondering if this will create problems.

I'm not too concerned, but it is a B+W and I've come to expect and respect the high quality of these filters. I also have an NL1 B+W closeup filter, which appears to be of newer manufacturing given it's side stamping.

Whether or not it ever causes a problem is immaterial. This is poor workmanship. Period. Exchange it.

Will not be a problen,but you can fasten the internal ring which hold the lens.

I do not have the rubber ring to tighten it, but no worries I had it exchanged! Thanks :D