64240 Set of Red/Blue 20’ Enviro-Guard Hoses for Automotive R-134A. Enviro-Guard Hoses for Automotive R-134a. Enviro-Guard Hoses are constructed of special barrier material which prevent virtually any permeation of refrigerant, yet remains flexible. Meet all specifications for low permeation construction. Clearly marked for R-134a. 740 psi working pressure, 3700 psi burst pressure.