Needle size

[Ashop]

for cidoteston 250mg

i have 23g x 1 1/4"
0.6 x 30mm

or

21g x 1 1/2"
0.8 x 40mm


Will either of these work?

And do i have to use 2 needles (one to draw up and one to inject)
Or can i just use 1 if im careful not to hit it on the bottom of the amp and blunt it.

Either would work. The 23g will be less painful,,since they are a finer gauge.