If you substitute one of the other phenidones; Phenidone B, Dimezone, or Dimezone S be aware that a 1:1 substitution will not produce the same developer activity. Not only must you compensate for the increased molecular weight but the substituted phenidones have a lower activity. So when substituting Dimezone S for Phenidone you should really use at least 1.4 times as much Dimezone S to produce a developer that has the same activity as the Phenidone version.