Detail 01
Single string, not a set
You get the D only. The other three stay as they are, so tone will not fully match if they are old.

Independent shopping perspective
Single D string from Thomastik's Dominant viola set, for 15-inch and larger violas. Replacement for a broken or worn D rather than a full re-string.

Strong match
Consider the trade-offs
What matters in use
Catalog numbers tell only part of the story. These are the details most likely to change how this product feels, sounds, or fits into a setup.
Detail 01
You get the D only. The other three stay as they are, so tone will not fully match if they are old.
Detail 02
Viola sizing goes by body length, not fractional size. Measure back-of-body before ordering.
Detail 03
Synthetic-core family rather than plain steel, so it settles in over days instead of holding pitch immediately.
Detail 04
The lower-middle string. Wear here shows up as dullness and poor response before it shows as breakage.
Final check
Product questions
Straight answers to the questions shoppers most often ask about this product.
Yes. This is the 15 in. and larger size, which covers 15, 15.5, 16 and up.
No. This is the D string alone. A, G and C are sold separately.
Synthetic-core strings stretch. Plan on retuning frequently for the first few days of playing before pitch settles.
Mechanically yes. Tonally the D will not blend evenly with strings from a different family, so most players replace by set.