I make my own Caverject: I ordered Alpostin (Alprostadil) from India and injected it into a bacteriostatic water solution, so I can dose it out properly.
I use a tiny diabetes needle and I inject about 15mcg, that is about 7.5mcg into each side of my cock.
About 15 mintues after the injections, it is as hard as a fucking rock. Harder than it should be. Even after I cum, it stays hard (depending on how much I inject). My cock is prone to getting erections even the next day, quickly, easily, and super-hard. It is the hardest hard it can be, pushing the cock to its absolute MAXIMUM size, which for me is 6.8 inches long, but also 6.4 inches in circumference (average circumference is 4.59 inches, BTW).
DANGER: Once I did a total of 35 mcgs (I don't go over 15 mcgs nowadays) and I had a boner for 3.5 hours and came a total of 3 times. My cock was sore for 2 days, not from the injections, but from being so damn hard for so long. That 3.5 hour mark was getting dangerous, my wife thought we'd have to take me to the ER to get it taken care of (4 hours and you need medical attention, or your dick might rot off.) but it finally started to recede. I never injected that much again. LOL
Below is a picture of some of my fun toys: the Alpostin box, the bacteriostatic water that the Alpostin is suspended in, the diatbetes needles I use, Viagra from India (sooo cheap), and a cock ring which is useless after injecting my home made concoction!