IM on fina and prop, injecting everyday. I love bi injections they hurt but there the shit. Fina alone is not bad, but add in the prop and its some serious pain. When ever i start a cycle that involves bi injections, after the first bi and tri injection my arms grow .5 to .75 inches. I know its just from the oil, but thay stay big. and just keep getting bigger. So i would recommend doing then. 25 Gage, 5/8 inch needles.