One of the first things many people notice when starting out with sashiko is that the needles look different. A sashiko needle is usually longer than a regular embroidery needle and also has a fairly large eye.
The extra length is no coincidence. When sewing sashiko, you often pick up several small stitches on the needle before pulling the thread through. This way, you can sew a longer line in one go instead of doing one stitch at a time. This technique makes the work both faster and more rhythmic.
The needle eye is also larger than on many other needles. This is necessary because sashiko thread is usually a little thicker than regular sewing thread.
Sashiko needles come in different lengths. Shorter needles can be handy for small details, while longer needles make it easier to sew long straight lines in the pattern. Many people choose to try a few different sizes to find the one that feels best in their hand.
In practice, it is possible to sew sashiko with other needles as well, but a real sashiko needle makes the technique much smoother.