Code example for http://roytomeij.com/2013/should-you-use-a-sass-mixin-or-extend.html

good_mixin.scss

@mixin border-radius($radius) {
  border-radius: $radius;
}

.foo {
  @include border-radius(5px);
}

.bar {
  @include border-radius(7px);
}

.baz {
  @include border-radius(9px);
}