建议翻译成：
I want to know when this kind of product came into the stage of the mass production.

因为,“the mass production stage ” 这种结构多在学术论文出现.

希望帮助到你,若有疑问,可以追问~~~
祝你学习进步,更上一层楼!(*^__^*) 建议翻译成：
I want to know when this kind of product came into the stage of the mass production.

因为,“the mass production stage ” 这种结构多在学术论文出现.

希望帮助到你,若有疑问,可以追问~~~
祝你学习进步,更上一层楼!(*^__^*)