Wood Violins Viper D string
These are the Wood Violins-branded D strings. The ball end of the string is red with a black winding. Any standard D string will probably work on the Viper, as the D string is on the short side of the angled tailpiece, but this is the D string that comes on any unfretted Viper. Fretted Vipers get (and Wood Violins recommends) the Helicore Titanium D string, which holds up better on fretted Vipers.