A combination of one soft and one hard aligner achieves about 0.6mm of tooth movement. Starting with a soft aligner ensures low initial forces, followed by a hard aligner for final adjustments. A study found that using progressively thicker aligners reduces force values and provides a consistent load increase for each setup step. Importantly, treatment time remains unchanged or may even be quicker, as a larger range of movement is possible compared to a single thickness aligner system.