The Straight 304 Stainless Steel Reusable Dispensing Needle is used with all ramé-hart goniometers and is supported on the Manual Syringe or legacy Microsyringe Assembly or any syringe that features an industry-standard male Luer lock fitting. Needles are 2" long. 22 gauge is the standard size. The smaller the gauge, the larger the diameter. 33 gauge is the smallest while 5 gauge is the largest. All sizes from 5g to 33g are kept in stock. If you are using this needle with our Automated Dispensing System, you will require the optional needle fixture. See https://www.ramehart.us/fixture-adapter/. For a detailed list of needle dimensions and sizes with part numbers, please go to: http://www.ramehart.com/pdf/needles.pdf Note that the p/n for this item is 100-10-12-XX where XX refers to the gauge, between 8 and 33. If you wish to add a beveled tip, add this item to your order: https://www.ramehart.us/add-bevel-to-single-needle/. If you require this needle in a specific length, then go to https://www.ramehart.us/resuable-304-stainless-steel-needle-custom-length/