3D PEN can devide into 2 types: regular 3d pen and low temperature 3d pen.
Regular 3d pen which use PLA/ABS filament(as same as 3d printer's filament). melting point is 190-230℃, so nozzle temperature is 50-60℃.
Low temperature 3d pen which use PCL filament(new filament only in China), melting point is 80℃. so nozzle temperature is 10-20℃.
So suggestion, if your customer has young kids, you'd better choose low temperature. But regular 3d pen still are the main market.
For DEWANG low temperature 3d pen, shape is cute, because it is for kids. Also we add much funny accessories, like emoji sticker. So it is for toy or for young kids,
3D PEN main function has 3 types: connect with adaptor, USB charging, battery inside.
Old 3d pen(V1, V2) need connect with adaptor always.
First improvement: X4, X4-2.0, D6, D7 can use USB charging, means you can connect with power bank/computer/adaptor or any device which can reach 2A.
Second improvement: battery inside. , D10 has battery inside, charging 20mins, you can use 1.5h.
D9, released on 2018
D11: The main advantage: it can load 3 colors filament at same time.