What size needle do I need?
here you go...
The smaller the gauge the larger the needle.
22 or 23 Gauge, 1.5 Inch is ideal for injections into the glutes.
25 Gauge, 1.0 inch is ideal for injections into the quads and can be used for all spot injections.
25 Gauge, 5/8 inch is often used for tricep/bicep/delts