Not sure why this didn't work very well.  The vanity counter is 5/8" glass or advanced cultured marble on a 1/2" or 5/8" inch melamine base.  The pop-up (as shown in the image) has about 3" of smooth plastic (not metal, BTW) before the spiral threads begin.  This made it extremely difficult to get a tight, connection.  Ended up substituting a universal pop-up drain from the local hardware shore.