Cross-section of the BTTRZ 4×16 mm² cable: a red low-smoke halogen-free oversheath, a corrugated copper sheath, and four 16 mm² copper cores each wrapped in mica tape and mineral compounds with compact inorganic filler, forming a concentric multi-layer fire barrier. Flexible yet mineral-insulated, the cable can be coiled and laid in one length without joints, suiting circuits that demand circuit integrity.