This adapter let you fit a cheap heating radiator thermostats with M30x1.5 screw mount to Danfoss RA (RA2000, RA-N etc) snap-on mount valve. Original Danfoss RA mount thermostats are pretty expensive and not readily available.
You need to fit it over valve and then tight it up with M3 screw and M3 nut. There are two catches that restricts adapter from rotating when screwing thermostat on, but you can rotate it by splitting it a bit and snapping to the next groove on valve.
You should print it with ABS because PLA would not hold with heat. Although I made an update with thicker walls and it may work with PLA, but I have not tested last one yet.
If you want just a working piece then you should print with ABS.
Danfoss RA valve
Danfoss RA valve with adapter installed
Danfoss RA valve with M30x1.5 thermostat
Danfoss RA valve with M30x1.5 thermostat, earlier revision