23G

23G is a designation used for hypodermic needle gauges and other small-diameter surgical instruments. The 'G' stands for gauge, a sizing system in which higher numbers denote thinner diameters. A typical 23G needle has an outer diameter of about 0.64 millimeters (roughly 0.025 inches), though exact dimensions vary by manufacturer and wall thickness.

In clinical practice, 23G needles are used for fine injections and for venous cannulation in situations requiring a smaller puncture, such as pediatric patients or fragile veins, and for dermatologic procedures and local anesthesia.

A notable use is in ophthalmology, where 23G instruments and trocars are used for vitreoretinal surgery. The 23G vitrectomy system introduced in the late 1990s and early 2000s allowed sutureless, smaller-incision surgery compared with older 20G techniques.

Compared with other gauges, 23G sits between thicker 22G and thinner 25G needles, balancing rigidity and ease of puncture. The actual inner lumen and flow depend on wall thickness and needle design; so diameters and performance vary by manufacturer. The gauge system is standardized to an extent but is not perfectly uniform across products.