D'Addario Helicore Cello set: 

Helicore cello strings are crafted with a multi-stranded steel core, resulting in playability while producing a clear, warm tone. The smaller string diameter provides quick bow response. Premium quality materials combined with skilled workmanship produces strings known for pitch stability and longevity.

Set includes:

• Helicore Cello A (H511): Titanium/steel, Medium Gauge
• Helicore Cello D (H512): Titanium/steel, Medium Gauge
• Helicore Cello G (H513 ) Tungsten-silver/steel: Medium Gauge
• Helicore Cello C (H514) Tungsten-silver/steel: Medium Gauge