See everyone is different...my ventrogluteal is very defined so I use a 27g 1/2 inch insulin pin and inject slow and comfortable and with hardly any PIP....but take note that I get my heating pad out and heat my oils up for 15-20 mins while I'm I n the shower and draw that watery oil up and pin it warmed....goes smoothly everytime....but now my bf is about 6-7%....so it will vary from person to person....u just have to get to know ur body and the best place to inject...bc my injection site varies from compound to compound....there are some I can put in my shoulders and others I can't...my most universal is my glutes and ventroglutes

And in case you need an awesome explanation by the coolest guy here

www.eroids.com/pics/ventrogluteal-injection

23-25g depends on what I grab from the stash and I've used as short as 5/8" on Ventrogluteal with no problems

i use 22guage or 23 guage 1 and 1/2 inch for glutes always nothing other than those two unless your bf is under 10% you need that length no questions asked