The new merlin hotend from Bjoern Marl http://www.merlin-hotend.de
To suit 1.75 and 3mm filament.
How much is it and what’s its advantage?
this kit costs 65 usd and you have 2 hotends inside, 1x 1.75 and 1x 3mm and you also have 3 nozzle, (0.2, 0.3, 0.5), 2x fan, 2x heater cardrige, 2x thermistor, 1x grove mount
And what’s the advantage of this hotend? I’m not so into hotends… that’s why I’m asking 
the advantage is the price because they are 2 hotends of different size for the price of one
can have option to choose 2 hotends with same size filament?
Ya ill likely never use 1.75 but it could be worth a try as a dual extruder kit if they are bothe the same size.
Yes Ryan you are right, this is also a possibility to add same of the same filament size.
@Ryan_Hescock_Stanos dual-extruder is still possible with different size filaments 
Cc @Bjorn_Marl
@Miguel_Sanchez yes im sure but for the sake of ease of calibration and sourcing I’ll stick with a common size.
Another advantage is that you can switch nozzle diameters easily and if for some reason the nozzle gets clogged you can exchange it for little money. The main reason why i made it was that i found most hotends at that time to not be reliable enough.