Micropipette pulling question

[taaustin at vaxb.acs.unt.edu]

I am using a Sutter P 87 micropipette puller to make microelectrodes for
intracellular studies.  I am consistently getting an uneven narrowing or "neck"
about 10 to 20 microns from the tip.  Is this detrimental, what causes it, and
how can I get rid of it, if necessary?

Thanks