Both! SuperCoils are a replacement to factory coil springs. SumoSprings are an enhancement to your suspension. Sagging or over worked coil springs should be replaced with SuperCoils. Vehicles needing additional load support and/or increased ride comfort should consider using SumoSprings in conjunction with coil springs or SuperCoils. Most popularly, SuperCoils complimented with SumoSprings Solo (in place of factory bump stops) are a great suspension solution.