I've seen some new guys on here who apparently think each AAS of your stack requires it's own syringe.
THIS IS NOT TRUE.
It is completely safe to inject multiple compounds at once, using a single syringe.
1. Wipe the tops of all the vials you will be drawing from with alcohol and allow them to dry.
2. Draw the correct amount of each compound into your syringe. A little simple math comes into play here, but you should be able to handle it. I like to use a 22ga needle for drawing.
3. Replace the needle you used to draw the AAS with a new, sterile needle. I prefer a 23 or 25ga for injecting.
4. Inject the AAS and discard of the syringe and both needles.
You can pin short and long esters in the same syringe.
You can pin different compounds in the same syringe (test/deca/tren/mast/primo/etc).
FYI I pinned 0.5ml each of test E, deca and tren A with 1ml of tren E last night. All in the same pin. No PIP. No abscess. No problem.
You DO NOT need to change needles for each vial, but you SHOULD use a fresh needle for injection since they dull very easily.
Here are a few pictures of used needles under magnification. These were used on flesh, rubber stoppers are much tougher.
You can think of each time into a vial as 1 use.