amanitadine
Bluelighter
23 g and .75 inch is the standard textbook line for I.M. injection but smaller gauge is fine (as long as it breaking off, bending, etc) and you can get in some muscles with a 1/2" or smaller needle. The deltoid, pectoral, etc in a non-fat person can be easily reached with a 1/2" insulin syringe.
