I just started my Syntherol Run yesterday for the first time ever & right now I'm using 27g Insulin Pins "1/2 (half inch), I shot my first 2 Syntherol Shots, .3cc in each head of my bicep (I know its not alot but I wanted to see how I reacted to it) because I need to get used to the long needle before I go sticking that far of a needle in my bicep, I would like to be using 1 inch but right now I only have 25 gauge 1 inch and I feel like it might hurt more (not a fan of needles if they arnt that long, the longer the more I hate it lol) . The injections were painless but I definitely felt the inflammation hours later, and considering it was not even half a cc and couldnt barely straigten my arm after doing my bicep workout, I'd say it'd definitely working, just gotta get used to the injection spots and do a little more research on Anatomy. I go directly off SpotInjections.com or Howtodoinjections.com/synthol/seo-synthol-guide-biceps/