Testosterone Decanoate CAS 5721-91-5 Testosterone decanoate bodybuilding, a.k.a. Neotest 250, is probably best known as one of the ingredients in Sustanon. Neotest 250 is testosterone with the decanoate ester, a slow-acting long ester, similar to testosterone enanthate. Testosterone decanoate commonly used in intramuscular injection solution, the oil absorption is slow, function is strong and…