The PHL marking system is intended only for insulation and not for any printing. The UL approved system with 2:1 shrink ratio features 100°C shrink temperature and 55°C to +125°C working temperatures. They are made of flame retardant cross-linked polyolefin material, flame retardant cross-linked polyolefin tubing fixtures and come in standard black. They are also available in other colors on request.