Centaur One-Way Barrel Tensioner 5" BlackCentaurs low profile tensioners mount unobtrusively to end or line posts, preserving the traditional rail appearance. Specially designed for 5 flexible rail, these tensioners are crafted from heavy duty steel and powder coated to help prevent corrosion. Barrel tensioners make installation and adjustments simple and fast. The block and sprocket design requires no special tools. Tensions with a standard 1 2 inch drive socket wrench. Designed to