I would like to try using French wire to finish my next necklace or bracelet project. I found some at Fusion Beads and it is made by Bead Smith.  It is silver colored or gold colored.   Has anyone ever used it?  Does the color stay true or does it tarnish?  Are there other companies that make French wire?  Does French wire come in sterling silver or gold filled and if so, is that necessary?  And last but not least, what size should I get.  One site I checked said to get .340 but I only saw it listed as fine, medium or heavy.  Which one would .340 be?  I really appreciate your help with this.

 Good questions, indeed. Yes it is available in S/S and GF.

To learn how to use it I suggest stopping my your LBS (Local Bead Store) , buy a small quantity and ask these questions. Or, Call up Fusion and explain that you are considering a purchase and ask How is it best used? 

French wire is classically used with knotted bead and pearl necklaces to protect the cord. There are new products that do the same. Beadalon's "Wire Guardian" or the generic "cable thimbles" are sold by many stores.

See Cable Thimble. 

I use French wire and love it.

I tried the bead/wire guardians but I find them restrictive and difficult to use (mabye that's just me, though).

Since I work with sterling silver, I buy sterling silver French wire.  I haven't yet found gold-fill French wire though.

The first thing I learned about it is that it comes in varying sizes and I apparently need the larger size (have some skinny stuff I can do NOTHING with).

Good luck!