Thanks again Rory for sending one of these new hotends my way! I've not had much chance to test out the mounting options in a real way yet, but i'll offer some observations. it's a pretty solid mounting option. Once the screw threads have been tightened down it won't budge. It certainly solves the problems of the groovemount. It gives some nice new alternatives to mounting as well, you can use groove adaptors, and then tighten down the nut to keep it in place. I had one of these groovemount plates lying around, unfortunately it was slightly too thick to get under the threads, and the diameter of the heat sink under the thread is slightly larger (12.4mm) then a standard groovemount (12mm), but a bit of work with a file for 10 minutes got it in. Perfect for a bowden set up, and very rigid. An interesting option, is that most well tuned printers can actually print screw threads really easily. Using fusion360, I designed a block with an M14x1 thread. It screwed in first time with no problems. Perhaps not the best mounting option, as it actually poses the same problems as a groovemount (wear over time), but you can buy machine screw taps really cheaply these days, so perhaps designing your own metal mounting system may not be as hard as you think. Access to a pillar drill and a steady hand is all you'd need now, whereas before you'd need a CNC set up or a lathe to produce your own groovemount. Now just drill a 13mm hole in metal, and tap it M14. Once I get an M14 tap this is likely how i'll mount the hotend. Although as a quick and easy option, the printed thread works really well. Its tight and solid, and it won't be going anywhere. Tighten it in with a set screw on the side and this is a very viable option still. Next up is the screw holes. Pretty simple and works well, however it seems overly bulky to me. Its also weighs more. The nut is a pretty solid chunk of metal, I've not weighed it but I can certainly tell the difference in my hand. The screws can also only be used in the top of the nut, you can't use them from underneath as the heatsink is slightly too large. I think this is what annoys me the most about this mounting system.... How do you use it with a direct drive extruder? If you could use these 3xm3 holes to screw it directly into an extruder, then that could potentially be useful (or perhaps just use the original m14 screw?) Why not place the M3 mounting holes in the fins instead? Get rid of the top 16mm, and just screw into the fins directly, perhaps this is the best way to keep the groove mount as well. You could simply have a heatsink with a thread on both ends, one thread is used for the heatbreak, and the top is used to screw in the optional groovemount or m14 mount. Remove it for 3x m3 mounting holes. Heres a quick render of what that could look like: Perhaps the best in terms of versatility?