The double-layer explosion-proof zipper is stronger than the ordinary single-layer zipper, and it is not easy to be opened. The ordinary zipper may be easily opened with a ballpoint pen, which is very unsafe, so more and more trolley cases are Switch to a double-layer zipper. Moreover, if the single-layer zipper trolley case is too full or squeezed, it may burst open, while the double-layer zipper is very tight and can effectively prevent the zipper from exploding. The double-layer zipper trolley case has no aluminum frame for impact resistance. The trolley case is good, this is a common problem of the zipper trolley case, but as long as the quality of the case is good, the effect is not big.