Head Gasket - TRD 0.8mm - 4A-GE 20 Valve EngineTRD Steel Head Gasket 0. 8mm for Toyota 4A GE 20 Valve Engine 0. 8mm Thickness With technology fed back from the racing field, TRD has improved the seal and durability of our cylinder head gaskets by changing the material and optimizing the surface pressure distribution. Also, by changing their thickness, we have made it possible to obtain the ideal compression ratio for improved performance. Note: We advise the use of ARP Head stud kit