Gland packing is a material used to control leaks, not to prevent the whole leakage, because the packing must always be lubricated and leakage recommended to maintain lubrication is around 40 to 60 drops per minute. The packing lubrication method depends on the condition of the liquid being pumped and also the pressure on a stuffing box.
Gland packing is usually made with braided or woven systems with a cross section shape and its constituent material can be graphite, acrilic, PTFE, asbestos and so on the liquid on the pump that serves as a lubricating gasket.