5.11 Tactical was developed in 1968 built on a foundation of durability, functionality and quality. 5.11 is a difficulty level in the Yosemite Decimal rating scale for rock climbing. With skill levels ranging from 5.0 (easy) to 5.10 (difficult); 5.11 is the most difficult. 5.11 is defined as this, After thorough inspection, you conclude this move is impossible; however, occasionally someone actually accomplishes it.