Quickly change the font-size of text. While our heading classes (e.g., .h1–.h6) apply font-size, font-weight, and line-height, these utilities only apply font-size. Sizing for these utilities matches HTML’s heading elements, so as the number increases, their size decreases. Quickly change the font-size of text. While our heading classes (e.g., .h1–.h6) apply font-size, font-weight, and line-height, these utilities only apply font-size. Sizing for these utilities matches HTML’s heading elements, so as the number increases, their size decreases.