PWX-3A, developed on the basis of original antimony mercaptide by our company, is a heat stabilizer specially used in production of PVC transparent hard products and semi-hard products, boasting sustained heat stability, good compatibility with PVC resin and good transparency. Secondly it also features non-toxic, less odor, no pollution, no migration and no frost. It has suitable lubricity, which especially is suitable for production technology of new type double-screw extruder. It is easy to use during processing and has good synergistic effect with organotin compound. For its low price, it can low the cost notably and is an ideal substitute for organotin.