Cypionax 200mg is a single-ester, long-acting form of testosterone. Due to the length of its ester (8 carbons) it is stored mostly in the adipose tissue upon intra-muscular injection, and then slowly but very steadily released over a certain period of time. A peak is noted after 24-48 hours of injection and then a slow decline, reaching a steady point after 12 days and staying there over 3 weeks time. A long-acting testosterone ester may be the best for all your mass-building needs, but it's not an easy product to use. Nolvadex and Proviron will come in very handy in such cases and post-cycle. HCG and Clomid or Nolvadex will be required as well to help restore natural testosterone.Frequency of side effects is probably highest with this type of product.