Thin Ca will flow through as small as a 30 ga. needle, but the needle is only good for one or two uses before clogging, the small needle allows good control of how much you're using.

once you get to thick Ca or white glue, a 22 is about as small as you can go and still get any glue out. Epoxy takes a 16 or 14 ga, which is about as big as a #2 pencil lead. The larger the syringe volume, the more injection pressure you can create, even if you only have a tiny amount to put in the syringe.

If you can get I.V. needles, they have both the metal needle as well as a teflon sheath that fits over the needle, sort of two-for-one. Spinal needles are great for long reaches, from 3 to 4 inches long, and epidural needles (called Touhey needles) have a tip that has the opening on the side at the very tip, but still has a sharp point.

Working in a hospital sure has its advantages.