These are the exhaust valve seats for lead free small bore cylinder heads
850/998/1100. If you require inlets see
TAM2152.
Fitted from 1988 with introduction of press fit high compression pistons although many earlier heads have used this modification.
Recess required is 1.1245"(28.56mm) plus or minus 0.0005"(13mm)and 0.190" (4.83mm)deep at room temp of 20C