This listing is for ONE Solid Plug. Solid: Problem: Too much ventilation is slowing you down. Solution: By sealing off the vent hole completely, your prop can now get the solid water it needs to propel through, optimizing performance and fuel efficiency. With PVS, now you can get Mercury performance, Mercury power and Mercury acceleration - no matter what engine you run. The Performance Vent System® is an EXCLUSIVE Mercury innovation that allows you to "custom tune" the venting of your propeller blades - giving you the power to adjust your propeller to the way you boat. The propeller is directly responsible for how your boat reacts in the water. PVSTM allows you to adjust for changes in load and environment simply by changing the propeller"s vent plugs for optimum acceleration. On acceleration, exhaust is drawn out of the vent hole. When the propeller blade strikes this aerated water, it pushes through it much easier than it would solid water - causing engine rpm to increase more rapidly. Once you"re on plane, the water flows over the vent holes and seals in the exhaust, allowing the propeller to again operate in solid, nonaerated water. Just by varying the size of the exhaust hole and controlling your engine"s rpm, you can eliminate sluggish performance or compensate for changes in load an altitude. And it"s technology that you can only get with Mercury Propellers.Propellers with PVS: Maximus Laser II Trophy Plus Tempest Plus Mirage Plus VenSura Revolution 4 HighFive Enertia