Genotropin Human Growth Hormone hgh is one of the best on the market. This is the newest presentation of Pfizer’s Genotropin rHGH 12mg 36 IU Easy Inject Pens. They are called easy inject pens because they're easy to set up and inject. The rHGH lypholized powder is packaged inside the pen in a clear plastic enclosure and above is the bacterialstatic water. This means that the shelf life of each pen is many years until activated. You combine the lyophilized powder with the bacterialstatic water by twisting the body of the pen in a 3 step process. The Genotropin Pens use a screw on syringe that is super easy to use for injections. They also have a twisting end piece that allows you to select the dosage you would like to administer and the pen will automatically calibrate to your desired dose. These really are the easiest to use.