There is two kinds of body filler in the market:

One is BPO (Benzoyl peroxide) system, Another is CHPO  (Cyclohexanone peroxide) system

BPO system: this kind of hardener system comes from Europe. It is very popular in most countries of world, like Europe, America etc. This type body filler can dry fast, and available to apply on most substrate directly, like galvanize steel, alloy, aluminum etc special substrate.

CHPO system: this kind of hardener system comes from Japan. It is popular in a few countries, like Japan, China, Malaysia, etc. The cost is very cheap. But the cure speed is very slow (the dry time is long), almost twice or thrice than BPO system. The cure speed is affacted very hard by environment (temperature and humidity). This type body filler cannot apply on galvanized steel, alloy steel directly,must spray epoxy primer first. The hardener has strong smell.

The most important point is the two different system cannot be interlaced used. It means BPO hardener cannot cure with CHPO putty, CHPO hardener cannot cure with BPO putty.