Plain Plug Gauge for Sleeve ID Go 8.303 to 8.305 Cyl. 0.001 Len. 50 to 51; with tapping of M4; NOGO 8.395 to 8.4 Cyl. 0.003 Len. 10 to 11 / Std. Gauging area should have lapped finish. Gauge No. PPG 8300.8400