I use either 0.5 ml or, preferably, 0.3 ml syringes. It is easier to get the right dosage because of the finer gradation of markings on the syringe barrel.
As to the earlier comment on 27 gauge needles having slow fill time, I have had no problem filling them relatively rapidly even using T in cotton seed oil, which is more viscous than, say, grape seed oil.
I was even injecting T, for a couple years, using 30g, one-piece insulin syringes. Yes, they take a while to fill, but I had a little rack to hold the bottle and syringe until it filled. You never notice the injection with a 30g needle. I am only using 27g now because of frequent travel and no travel friendly rack .
Also, with a thinner needle, you can use a needle clipper, which really simplifies disposing of the spent needlesā¦ really nice for traveling.
Lastly, these are all one piece, so no need to change needles and no loss of product as in the case of two piece syringes.