The ornamental design for a headlight for vehicles, as shown and described.
1. Headlight for vehicles
1.1 : Perspective
1.2 : Front
1.3 : Back
1.4 : Top
1.5 : Bottom
1.6 : Left
1.7 : Right
1.1 is a front, top and right side perspective view of a headlight for vehicles, showing our new design; 1.2 is a front view thereof; 1.3 is a back view thereof; 1.4 is a top view thereof; 1.5 is a bottom view thereof; 1.6 is a left side view thereof; 1.7 is a right side view thereof; the broken lines in all views are shown for illustrative purposes only and form no part of the claimed design; the alternate long and short dash lines in all views show the boundaries between the claimed design and the others.