Standard slides are for four-legged tables. As you open your table to add leaves, these slides automatically bow up to counter the natural tendency of the table to sag in the middle.Equalizer slides are geared for pedestal base tables. The gear causes them to open in both directions at the same time balancing the weight evenly. They also have a built-in camber to counteract the tendency to sag when extended. Slides are provided with square drive-mounting screws for easy assembly. Sold as one pair per unit.