I use 30G, 8mm, .3cc and 31G, 6mm, 1ml and surprisingly the difference between the 30G and 31G is a matter of minutes. The 30G pulls way more easy. But still even with the 31G its just 3-5 minutes job from cleaning vials to pulling out the needle from the upper glute. I pull in Grapeseed, arachid oil and liquid based Test and HCG in one single syringe without any issues.