The Ergo 4012 grip spacer fills the rear upper void on large frame AR15/M16 rifles. 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.