DESCRIPTION â??️ Plain String All plain strings feature a series of lock twists to secure the wire around the ball-end, preventing slippage and ensuring a long-lasting string. â??️ Core Wire The core is made from brass plated high carbon steel hex wire providing excellent durability. â??️ SIX SIDES OF STABILITY. Precision drawn hexagonal core was pioneered by 5 Core. This innovation allows the wrap wire to grip the core for superior dimensional stability, enhanced durability, and precise intonation. â??️ EXACT STANDARDS, EXTRAORDINARY SOUNDS. 5 Core in-house wire drawing machines produce musical instrument wire to our exact specifications. Control over materials, equipment, and quality allows us to deliver high performance products.