UTC is available in Extra Small or Midge, Small, Brassie, Medium and if memory serves me right, Large which is not much good on anything less than a 6/0!
Probably the best generally available wire on the market and as Midlander says in his ElectroStatic Buzzer post, the best colour holding when SHHAN, epoxy or superglue is applied as most others have colour run when you do this.
I have some UNI wire in a few colours that I never use as the majority of what I have is UTC, this lot being mixed sizes.