Here's what D'Addario say about the Chromes ECG26 Flatwound Strings:
ECG26 is D'Addario's heaviest gauge of flat wounds. This set delivers smooth feel, warm/mellow tone and maximum tension. XL Chromes are noted for their smooth feel and warm, mellow tone, essential to the sound and style of many jazz, blues, and rock players.
D'Addario XL Chromes are the industry standard in flatwound guitar strings. They deliver a round, full low end without losing punch, making them ideal for jazz players of all types. Wound with flattened stainless steel ribbon wire, XL Chromes are then polished to unparalleled smoothness.
Flat wound strings feature precisely flattened stainless steel wrap wire that is wound and polished to provide an ultra smooth feel and full, mellow tone.
Precision drawn hexagonal core was pioneered by D'Addario. This innovation allows the wrap wire to grip the core for superior dimensional stability, enhanced durability and precise intonation.