Responsive helper utility is used to allow browsers to determine video or slideshow dimensions according to the width of their containing block in a way that it will properly scale on any device.
You have to apply rules directly on <iframe>, <embed>, <video>, and <object> elements; optionally use an explicit descendant class .embed-responsive-item when you want to match the styling for other attributes.
These utility classes are used to float an element to the left or right, or disable floating, based on the current viewport size using the CSS float property. !important is included to avoid specificity issues.
These use the same viewport width breakpoints as the grid system.
There are two similar non-responsive Sass mixins (float-left and float-right) are also available.