I got a Rx for Trimix today and I believe the needle is 30g - 1/2 inch. I thought about it afterwards, isn't a 1/2 needle too long? I don't want to inject it into my urethra. she must think I'm "girthy".
Just make sure you press hard on injection site and "milk" your penis to distribute the liquid and not allow it to remain in one spot. That would get in the way of efficacy and also potentially cause hard fibrosis spots.