Robinair ROB34722 9 ft. Red-Blue Enviro Guard Hose Set for 34788 - 34288 - 34134Z - 2 Piece Set of Red/Blue 9ft. Enviro-Guard Hoses for Automotive R-134A. Enviro-Guard Hoses for Automotive R-134a. Enviro-Guard Hoses are constructed of special barrier material Meet all specifications for low permeation construction. Clearly marked for R-134a. 740 psi working pressure&#44; 3700 psi burst pressure.