Oval Firewall Grommet, Early XK-150 With Cable-Driven Tachometer. This grommet is located in the firewall and is not listed in the Jaguar factory spare parts manuals. Overall size is 1-3/4" x 2-1/8" and 7/16" thick. The hole it goes into would be 1-3/8" by 1-7/8". All are approximate dimensions.