Edelbrock Performer RPM II Dual-Stage Nitrous System #70083 is designed for those who want to add power in stages to soften the “hit” of the nitrous system. This is one of the best ways to control excessive tire spin or violent chassis reaction. Performer RPM Dual-Stage Systems allow you to tune the first stage to supply 100-200 additional horsepower, then switch to the second stage for 200-400+ horsepower. Precision EDM machined spray bars for the best flow characteristics available. This system is for use with 4500 Series carburetors.