Standards ISO 34-1, ISO 6383-1, EN 495-2 and DIN 53363 relate to tear tests on plastic foils. The test simulates the behaviour of packaging foils when the package is opened. When opening a plastic bag, the initial tearing strength should be approximately as much as the remaining tearing strength. If the maximum force at initial tearing is too high, the danger exists that the plastic bag will suddenly tear open completely and the contents will spill out. The ideal behaviour is not easy to adjust because the tear resistance (as well as the tensile strength), is very direction dependent with stretched foils.