Spiral/Tungsten wound. 
Thomastik Spirocore cello strings are constructed with a flexible, multiwire spiral rope cope. They offer a distinctive open tone and easy playability. 

Features: 

• Thomastik Spirocore strings are constructed with a flexible, multiwire spiral rope core. 
• They are recommended for intermediate to professional players. 
• Distinctive open tone and easy playability. 
• Highly responsive across all strings.
• Available in three different material windings. 
• Tungsten is the highest quality winding available.