He and his wife Liz owned a boot and clothing company, Royal Robbins LLC, and began manufacturing specialty pants by the name of "5.11" in 1968, which had a trademarked strap-and-slash pocket design.

[1][3][4] The name "5.11" comes from a high level of climbing difficulty listed in the Yosemite Decimal System, which Robbins helped develop in the 1950s.

[6] Robbins sold a 51% stake in his company to Dan Costa in 1999,[7] who, after much streamlining, noticed that the 5.11 pants were becoming popular at the FBI Academy in Quantico, Virginia.

Partnering with the FBI, Dan Costa and his co-partner Francisco Morales began creating additional tactical apparel and improving on the existing product line.

[1] In the episode "The Truth Has a Ring to It" from the second season of the HBO series Barry, Monroe Fuches (portrayed by Stephen Root) is seen wearing a 5.11 backpack.