DIN 3866 is the male UNF thread with 90° flared end for solderless compression couplings rated for PN 40. It is used in refrigeration, with NPT threaded stem adapters, with flared 90° flared tube ends.
DIN 3866 Male UNF 90 deg flared end fittings size as follow:
DIN 3866 NPT male stem adapter size as follows:
DIN 3866 falred 90degree flared tube as follows: