These are the same machined aluminum injector seats used in many Radium Engineering fuel rails. They are required when converting the OEM fuel injector to aftermarket fuel injectors. They simply press-fit into the intake manifold/TGV injector ports with no modifications required. Using the included FKM O-ring, they seal into the machined injector counterbore preventing vacuum (or boost) leaks. The injector seat bores are designed to be used with a common 14mm lower injector O-ring.
All injector seat styles use the following lower injector O-ring measurements shown. Measure before ordering.
Features
-CNC machined 6061 aluminum
-Laser etched logo
-FKM O-rings
20-0305-04 SUBARU INJECTOR SEAT KIT, 26MM 4 CYLINDER
20-0305-04 is used to convert side feed injectors to top feed injectors. They are black anodized, as shown below. 
COMPATIBILITY
All SUBARU EJ engines (that came with side feed injectors) excluding 04-06 EJ257