The Ergo 4751 10 slot Polymer M1913 RAIL does not require alteration of AR hanguard heat shields. Unified in the mission to provide military, law enforcement, citizens and shooters with the finest mission enhancing firearms accessories available, the people of ERGO have grown their business through a combination of precision manufacturing and exemplary customer service. All ERGO products are 100% manufactured in the USA to the highest standards and the tightest possible tolerances. Expanding far beyond industry standards, every ERGO product is backed by a comprehensive satisfaction guarantee..