What does the s mean in a 22s or 26s gauge needle?
The "s" represents a smaller inner diameter for the needle and a thicker needle wall for better durability. For example, a 26 gauge needle has an outer diameter of 0.46 mm and an inner diameter of 0.26 mm while the 26s gauge needle has an outer diameter of 0.47 mm and an inner diameter of 0.13 mm. The 26s has half the inner diameter of the 26 gauge needle. The difference in the wall thickness also nearly doubled with 26s gauge having a thickness of 0.18 mm while the 26 gauge is only 0.10 mm.