Appion MH380004AAY - 3/8 diameter. Hose, 4 ft., 1/4FL to 1/4FL, Yellow Vacuum Rated to 20 Microns Larger inner diameter for superior performance Rated for use with R410A and all common refrigerants. All hoses are available in custom length, color and fitting combinations. Each hose is tested and evacuated before shipping. Larger hoses for system evacuation. Even when restricted by 1/4 system ports, using a 3/4 system ports. 8 or 1/2 Hose 2 greatly reduces resistance and increases potential flow. This is especially true during system evacuation. Just using a 1/2 hose with 1/4 fittings can result in one-tenth (1/10) the evacuation time compared to using a 1/4 hose. Or look at it another way: using a 1/4 hose can make a evacuation take up to 10 times longer than when using 1/2 hoses!