Custom device scope SASS

When you are working with responsive web design you need to deal with a buch of dimension, but using sass (.scss) you can write them into variables and call them as a scope:

$small-device: "all and (max-width: XXXXpx)";

@media #{$small-device} {
    .col1, .col2, .col3, .col4, .col5, .col6, 
    .col7, .col8, .col9, .col10, .col11 {
        float: none;
        width: 99%;
    }
}