These strings are an alternative to more costly and problematic gut strings, that are developing a cult-like following with many jazz, rockabilly and bluegrass musicians. Their design is what sets them apart, rather than a solid core or steel coating… well, how about I let them tell you about it: “First is the inner core which is a braided cord consisting of steel and silk. Silk is the key to the low tension, gut like tones and the steel adds tuning and intonation stability while adding the ability to work with magnetic pickups. This cord is then tightly wrapped with a blend of non-ferrous and noble metals (copper, nickel, zinc, tungsten, etc.). Finally, they are wrapped with a specially shaped and ground polymer with no color additives giving Eurosonic’s a unique, almost translucent look. Eurosonic Bass Strings have a gauge that is comparable to many old gut strings (new gut strings are MUCH thicker as they have not yet stretched).” Bottom line, they are a nice alternative to gut, and have a thick attack and less pronounced sustain than some other strings. Their Polyamide (what?!?) wrap, whatever that is, makes for a gentle experience for both hands, and though bowing isn’t great, it can be done. If you play slap rockabilly, or prefer a very low tension string, choose the Ultralights. However, if you play classic jazz, or do a mix of all styles including slap, I’d recommend the Lights, as the Ultralight strings can be a little slack for normal clarity. The Mediums are a higher tension that may not be desirable given this string’s basic design goal, but I also carry them for those that prefer a stiffer string with the vintage character of these unique strings. String Gauges G D A E Ultra Light Tension .065 inches, 1.65mm .088 inches, 2.25mm .100 inches, 2.55mm .130 inches, 3.30mm Light Tension .069 inches, 1.75mm .094 inches, 2.40mm .110 inches, 2.80mm .142 inches, 3.60mm Medium Tension .075 inches, 1.90mm .098 inches, 2.50mm .122 inches, 3.10mm .150 inches, 3.80mm Color codes: Ultralight: yellow with red stripe at ball end, solid yellow with red band at headstock end; Light: yellow with aquamarine stripe at ball end, solid aquamarine at headstock end; Medium: yellow with black stripe at ball end, solid red with black band at headstock end.