TEST PROP 100 100mg x 10ml (Gen Pharma) is Testosterone Propionate, which is a common injectable derivative form of the primary male hormone, testosterone. The added Propionate ester slows down the rate at which testosterone is released from the injection site. Therefore, Testosterone Propionate is faster than other testosterone esters, such as Cypionate or Enanthate, and requires much more frequent dosages. As an injectable testosterone, it is a mass-produced drug that can quickly increase both muscle size and strength. Testosterone Propionate is a modified form of testosterone where the carboxylic acid ester (propionic acid) is attached to the 17-beta-hydroxyl group. The half-life of Testosterone Propionate is approximately two days after injection.