POM (Polyoxymethylene) aka Delrin is a very strong plastic with properties similar to metal.

The joints on the Yamato 1/48 Valkyries connecting the front and back torso halves are POM.

It's becoming the new "it" material for toys instead of diecast metal. I imagine it's more expensive than ABS or PVC and usually only used for joints or parts that are subject to stress or lots of movement.

Ah, thanks.

It's hard sometimes to differentiate between some plastics, since I can't find solid descriptions of what they are or where you find them in toys; I sometimes have to guess what the materials are and hope no one complains or harasses me about it! ZincPanic.com wrote an article on them one time, but when I wrote them for clarification, they didn't respond. I know that ABS is a common hard plastic that doesn't flex unless it's really thin; and PVC is a softer plastic which can sometimes flex in normal thickness, but is lighter than ABS. Die-cast is obviously metal. But beyond that, I don't know. Someone help!
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CollectionDX Staff

Wikipedia and plastics manufacturer websites have plenty of info.