FIG. 1 is an upper perspective view of a dual-tip highlighter showing my new design;

FIG. 2 is a left side elevation view thereof;

FIG. 3 is an enlarged top plan view thereof;

FIG. 4 is a front elevation view thereof;

FIG. 5 is a right side elevation view thereof;

FIG. 6 is an enlarged bottom plan view thereof; and,

FIG. 7 is a rear elevation view thereof.

The broken lines showing portions of the top and bottom are included for the purpose of illustrating environment and form no part of the claimed design.