ORIGINAL: Zeeb
There's another vendor who they talk about over on FG, but I don't remeber the name right now. I've had really good luck with MPI extensions and they run all the way up to 20g. wire and all of them with gold plated connectors. They are quite reasonable compared to say Futaba or JR branded as well as being bigger wire than those two both of which have 22g. wire in their HD servo leads.
http://www.maxxprod.com/mpi/mpi-3.html
+1
I have been using them for years. They also have Universal extensions if you need to convert Futaba to JR/Spektrum (without carving up the Futaba connector). Some Rx batteries come with connectors that fit very tightly in Rx servo ports. I use short extensions, between the Rx and the servo, to avoid having the servo port take the wear.