I bought a Meerschaum pipe while stationed in Germany in 1982. Yellow stem and very nice and intricate carving. Smoked it a few times, cleaned it after smoking by running a pipe cleaner down the stem and that is about it. NEVER took it apart. Put all of my pipes up over 25 years ago and now getting back into it. Lots of oxidation on my other pipe stems and while taking the stem off of the meerschaum, noticed it had a small plastic tube coming out of the stem which fit into a larger white plastic tube in the pipe itself. Is this normal? I had always assumed the yellow stem would be like others...narrower portion of the stem that fit in carved out portion of the pipe. It smokes great, just don't know anything about it.