Plain Plug Gauge for Sleeve ID Go 8.1 to 8.103 Cyl. 0.001 Len. 50 to 51; with tapping of M4; NOGO 8.155 to 8.158 Cyl. 0.001 Len. 10 to 11 / Std. Gauging area should have lapped finish. Gauge No. PPG 8100.8158