2 Pieces, purchased from Jon Myers. The bracket is bolted to the drivers side front carb stud. This may require you install a longer stud. The dashpot is then inserted in the bracket and using a channel lock pliers, crimp the bracket to hold it in place. The adjustment is made holding the large metal stem with one wrench while turning the small hexagonal tip with another. The end of the larger stem is relieved so you can hold it with an open end wrench. CAUTION: If you turn the larger stem, you can tear the diaphragm and ruin the unit. After mounting the unit, connect the vacuum line to the convenient drivers side port on the Edelbrock carb. This is the full vacuum port. The passenger side port is timed vacuum and is where your vacuum advance should be connected to. If you are not using an Edelbrock, you can access vacuum at the rear of some manifolds, where a pipe plug is installed. Bring the engine up to operating temp before making the adjustment. Once things have settled down and the idle is suitable, back the small tip out of the stem and bring it up to almost touching the throttle linkage. test by blipping the throttle by hand. The rpm should drop smoothly with the help of the dashpot. If the engine idle fluxuates, you can see the dashpot react to the various levels of vacuum. This little piece works wonders especially if your engine loads up after a hard run and tries to stall at a traffic light. This was also a retro fix by the factory, for A/C cars.