Asianlover, usually it's b/c adding two esters that are longer allows for higher concentrations with less solvent. In the case of enth/cyp though, it's pointless to me. Cyp is much harder to get into solution than BA, so usually cyp/enth preparations will hurt. Straight enth at 500mg/ml barely stings, or is painless. Cyp usually won't go above 300mg/ml without a little kick. With longer, more soluble esters like decanoate, etc, mixing esters is just a trick to try and get higher concentration with less solvent, which should mean less pain. I stick with straight enth myself, or straight cyp, at reasonable dosages.