MIFAB® Series MI-FLEX-SO (specify size) of flexible rubber couplings are manufactured from neoprene compound that meets the requirements of ASTM C-564 and 300 Series of stainless steel clamps tightened with 5/16" Type 300 stainless steel hex head screws. MI-FLEX Series of flexible couplings are tested and certified to ASTM Standard 1173-2010 and CSA Standard B602-2016 and listed with I.A.P.M.O.