I don't know what is in DR's kit, but if you are looking for a heavy duty thread, buy a spool of Spiderwire braided line in 50 or 80 pound test. You can get it at Wal-Mart and just about anywhere that sells alot of fishing equipment.

It is incredibly strong and very thin - the 80 pound test is about the same thickness as regular 10 pound fishing line. It is strong enough to use to tie off a tarp if need be as well as small enough to sew on buttons.

One caveat - it is very slippery and you have to know how to tie a couple of good knots. (There should be an instruction sheet in the spool box. If not, you can google knots for it.) If you just tie a hitch, it will slip out.