Oubao Security Technology Co Ltd Established in 1987, ISO9001 system certified factory, We are largest door closer manufacturers in mainland China. Our factory also is the first factory in China who past UL 10C fire test in 2002. CE approved in 2004, ITS - PT test in 2005, We are ISO9000:2000 approved factory since 1998. We obtained the UL file since 1995.