Featuring unrivaled aesthetic options, cost saving versatility and proven wall performance, installer’s prefer the Compac′s lighter weight and shorter tail design which make it easy to handle. Keystone Compac III unit utilizes the proven Keystone pin connection system (2 pins needed per block) which can allow for either a near vertical or battered setback design. Allows for positive connection with reinforcement to build engineered walls over 4′ high.