Needles come in a large variety of gauges and lengths. Hubs can be plastic or metal. In our equine veterinary practice, the two most commonly used gauges for injection are 18 and 20 gauge. The best length for intramuscular injection is 1.5". For foals, 22 gauge or 20 gauge x 1" is suitable. Needles are kept capped until use, used once and discarded safely. Needles should not be thrown in the trash but should be discarded in a sharps container. Talk to your veterinarian about how to dispose of your used needles and syringes.