Injection needles are what you’ll attach to the syringe to draw up the oil and inject it. There are two main types you’ll be using: intramuscular (IM) needles and subcutaneous (subq) needles. These differ in two main ways: gauge (thickness) and length.
The gauge of a needle represents the length of its diameter. A needle with a smaller gauge has a wider diameter, while a needle with a larger gauge is narrower. As you may have guessed, needles with smaller gauges (18G - 25G) are used for IM injections, while finer needles with larger gauges (25G - 30G) are used for subq injections.
Additionally, intramuscular needles are longer because they’re designed to deliver the injection deep into the muscle. Subcutaneous needles are shorter and thinner, made for injecting just beneath the skin into the subcutaneous layer (also called the hypodermis), which is rich in fatty tissue.
I've included a list of trusted needle sources below, including Amazon links and brand names for convenience. Don’t stress over brands; they’re all reliable. The list just provides more context to help you make an informed choice.