The BD Ultra-Fine™ III Short Pen Needle is 31 gauge, 8 mm (5/16″). No pen needle is thinner. It is BD’s best-selling pen needle. The majority of people who take insulin – 82% – get effective results with this needle, but some people, many of whom are overweight, do not.* You should consult with a health care professional before switching to a shorter pen needle. Paper tab and inner shield are color-coded blue for easy size/gauge recognition. Today’s insulin needle is thinner and more delicate for greater comfort, so needle reuse can damage the tip and cause injury. Non-toxic. Non-pyrogenic. Short inner shield. Puncture resistant outer needle shield.