Cylindrical Stoppers is an inflatable bag with a rugged waterproofed casing which when inflated to high internal pressure will hold against 10 lbs. pressure in the pipe. The broad central zone makes contact with the wall of the pipe and holds against higher pressure than other types of bag.

Cylindrical Stoppers should not be inflated over the pressure given on the direction card fastened to each stopper. The pressures are as shown in the table below. These inflation pressures leave a margin of safety. They are about half the breakpoint under test in shop. Cylindrical Stoppers when inflated according to these directions will hold against pipe pressures equal to 60% of the pressure in the bag. A six inch stopper, for example, when inflated to 15 lbs. will hold back about 10 lbs. pressure in the main.