Specifies the style of arrowhead used for drawing links.

The default is 'classic' which has a wide arrowhead. You can also choose 'compact' which gives narrower heads.

Finally, you can get finer control by adjusting the size yourself. The width and length of the head are in units of link-width.

Classic is equivalent to '4 2' and Compact is equivalent to '1 1'.

Classic arrow style

Compact arrow style