The smaller the gauge of the needle, the larger the diameter.
Please refer to the chart below for syringes with needles:
New York Residents: If you wish to purchase syringes and/or needles your order must be accompanied with a State "Certificate of Need" or a prescription from your veterinarian. In New York state, obtain a certificate by writing:
Residents of CA, DE, CT, IL, MN, NH, NJ, or NY, please ask your veterinarian for a prescription to purchase needles and syringes. Any licensed veterinarian can provide you with a prescription. The easiest way to get a prescription filled is to ask your veterinarian to call us at 1-800-447-3021 or Fax to 800-447-2404 with the prescription information.