These adapter fittings are available in 3/8" and 5/16" sizes. They push-on and secure to most modern USA, European, Japanese, etc. fuel injection systems and are used to convert an OEM SAE Quick Connect hard line connection to -6AN male or 5/16" barb. 

The unique Radium Engineering adapter (20-0290 AND 20-0291) interfaces with a SAE Quick Connect male fitting in an ultra-low profile manner. The design uses a dual viton O-ring seal for a leak free connection. The retaining clip is held on with a stainless steel screw and is easily and quickly serviced.


Reference the picture below for the complete offering of SAE quick connect adapters:

To determine the required size, simply measure the outside diameter of the male fitting as shown below.
.375 = 3/8"
.3125 = 5/16"
 

IMPORTANT: Always lubricate the mating O-rings with a light amount of oil prior to installing.