Thomastik Dominant viola D string, medium gauge (mittel), Catalog #137.
Aluminum or Silver wound over a Perlon core.
For most 15” - 16.5" violas with about a 14.5” vibrating string length. If the vibrating string length (measured from the lower edge of the nut to the top edge of the bridge) is longer, you should order the next longer size strings.
“DOMINANT strings are highly flexible, multi-strand synthetic core strings known for their tonal warmth and gut-like feel. They are impervious to changes in humidity, allowing for stable intonation and long life. The sound is soft, clear and rich in overtones. DOMINANT strings, widely recognized as “the reference standard”, are legendary for distinctive tone and playability.” (according to Thomastik-Infeld)