Ming has created this post
How do you source a plastic injection mold maker in China
https://penzu.com/p/66dbb2f6
Plastic injection molds are generally constructed from pre-hardened or hardened steel, aluminum, and/or beryllium-copper alloy. Steel molds cost more, but are generally preferred because of their top durability. Hardened steel molds are heat treated after machining, and they are by far best in terms of wear resistance and lifespan.