The W87 design includes all modern safety features, including insensitive high explosives LX-17 and PBX-9502 (primary component TATB), a fire resistant pit, and advanced arming and fuzing safety features. The original yield of the W87 was 300 kilotons of TNT, but has the announced ability to be upgraded to a yield of 475 kilotons, presumably by using more HEU in the fusion secondary stage tamper. It is not known if that upgrade was completely tested or merely designed and ready to implement.