There are single (non performance) springs; Single w/dampener(performance); Dual, which have a large outer, a dampener, and then a smaller inner(higher performance); Or triples, which have the single outer, a middle, and an inner spring. You can use a stock type retainer for singles (stock) and singles with a dampener, but you cannot use a stock type retainer for dual springs, nor can you run a dual spring on the factory cut spring seat or use a factory type valve seal.