This is the idle mixture (bypass) adjusting screw for the Weber 32/36 DGV carburetor. It is used to adjust the amount of fuel flowing through the idle jet. If your idle mixture never seems to be right, check for a worn taper on your idle mixture screw.
Fits 32/36 DGV, 32/36 DGV 5A, 32/36 DGAV, and 32/36 DGEV. Does not fit DFV or DGS series. M5x0.5 x 14.5mm long thread with 3.5mm long shoulder and 3.5mm dia x 8mm long straight section between thread and taper.