Pressure fuel caps are recommended for aerobatic installations. These caps are made with Buna-Nitrile gaskets for fuel resistance. These caps are non-vented for gravity fuel systems. It is highly recommended that a #40 (3/32") drill is used to drill a vent hole through the lower base plate and stud assembly using a drill press. 

The dimension referenced on these pressure fuel caps is the OD of the rubber grommet around the neck (base).

Size: 2 Inch