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where is I can found instructions for this upgrade ?

So you're swapping out the stock hotend for a groove mount one?

While I haven't used their precise one, I do have one we made that's very closely related (While we didn't trace it dimension for dimension, we did look at it while we designed it. It should work vaguely like this slide your hotend into the wide section of the teardrop, then move it into the center. After that, screw the top portion on, and then mount it to the tops of the stand-offs like normal (I found adding one of the nylon spacers under it helped as well). The surfaces should hopefully be tight (Ours loosened over time dimensionaly, so I bought an aluminum mount instead, which is more expensive but more consistent and much nicer)

How you can see EZ Groove Adapter have a 4 screws.
I'm use 2 and don't know what to do with 2 others

[img]https://cdn.shopify.com/s/files/1/0276/ ... 1382621154[/img]

I don't think that these holes do anything anymore, and I can't remember what they were for on the original design...
[img]http://i.imgur.com/SlAaNJF.jpg?1[/img]



The important screw holes are the 3 for mounting, and the 2 with the longer screws for clamping the hotend in place.

Looks like a mount for a fan duct to me.