The 4" lift system uses replacement Select series front springs. Different weight-rated front springs are offered for both gas V-8 and heavier diesel and V-10 engine equipped trucks. Heavier springs are needed for the larger power plants' increased weight, while the lighter-rated gas versions considerable improve the less weighty truck's ride quality. These lifts utilize new Urethane compression travel stops for the front; the factory rear stops are relocated A Select Series spring, because of the increased overall pack thickness, requires less arch to provide a given lift height. This reduced arch generates less friction between the individual leafs. Anti-friction pads, placed between each leaf, further reduce inter-leaf friction, which in turn, improves ride quality. How much compression travel is allowed, and how abruptly this downward travel is stopped, is another important factor in the ride quality equation. With most manufacturers, compression travel management is not a serious consideration, if it is considered at all; not so with Superlift... the correct amount of travel, properly dampened by a new Urethane stop, has been calculated for each Superide Select system. For each lift height we have designed springs for both the gas V-8 engines and the heavier diesel Powerstroke and V- 10 applications; no "one-rate-fits all" mentality here. All of the Superide Select springs also feature military spring wraps (double-wrapped eyes) for enhanced safety and factory-style rubber bushings for superior durability. In summary, the Superide Select series springs are by far the best-riding and most durable leaf springs on the market. The remaining lift components are top-grade as well making the Select series systems as good as it gets.