Deaver U402 Progressive Series springs are high-quality 9-leaf units fabricated with high grade 5160 “American Made” steel designed for the Tacoma 2WD / 4WD. A higher leaf count spring allows the use of thinner leaf material that yields a more flexible progressive leaf stack, or pyramid, producing a much smoother spring rate curve throughout the complete suspension cycle. The even, linear compression rate curve of our progressive system spring is the primary key to excellent ride quality.