Fracturing machines, namely, a customized assembly for isolating and providing a selectable flowpath for the introduction of a fracturing fluid into multiple zones of a subterranean wellbore that features one or more tubular frac sleeves; ball seats and balls that are capable of closing the ball seat, sold as a unit

services which permit multi-stage fracturing of the wellbore including setting in a wellbore a liner string including a series of zone-isolation packers and sliding sleeves, introducing successive, sized blocking elements (drop balls) into the liner string to block the flow of fluid and open successive sliding sleeves in order to direct the fluid into the formation, especially when pressurized fracturing fluid is introduced into the wellbore