Insulin syringes: 31-gauge, 8mm are standard. Easy Touch and Comfort EZ are popular brands. Always use U-100 syringes—never U-40 (the math is completely different, like imperial vs. metric).
Luer-lock syringes: Allow changing the needle between drawing from the vial and injecting (a fresh, sharp needle for injection).
Pen devices: Increasingly popular. Filter into a pen cartridge instead of a new vial, then use fresh 33-gauge pen needles for nearly painless injections.
[Warning] Important:
Do NOT use syringes for storage. Syringes are not designed for long-term storage—don't pre-draw doses for travel. Draw your dose fresh each time.