Synthetic gut is nylon, nearly always composed of a single filament. It is a very inexpensive string to manufacture and is generally the least expensive string.

Small changes from pure nylon are usually found in strings sold as “synthetic gut”. Textured coatings, colorants and the addition of a small amount of Kevlar are the most common changes. Some manufacturers, such as Gosen, label nylon strings with words like “sheep”, as in sheep intestine, although such strings contain no gut.^[8]

Synthetic gut, as it is used for mono-filament nylon strings, is now a misnomer, as the creation of multi-filament strings has provided players with a better approximation of natural gut’s performance. Modern “synthetic gut” is actually a multi-filament string that holds its tension extremely well and which has a dynamic stiffness profile that is closest to natural gut, although the industry continues to apply the term to mono-filament nylon strings.