Needles are made of steel. But if a sewing needle made of this famously hard material is just hard, it will not satisfy. For the smooth passage of a needle when sewing, it must also be flexible. But as well as being flexible, it must also have a strong core; if it does not, it will break or bend and become difficult to sew with. Hardness is prone to being brittle; softness is prone to bending. Combining these two seemingly contradictory properties is a very difficult task. Techniques that make it possible have been added over time to the tempering process, which is still used today.
If they are hard yet yielding, and have an aesthetically pure luster, then we can call them Chuubei needles.

The eyes of Misuya needles are made as close as possible to perfect circles. Answering the challenge of how large a hole can be made in the thin body of a needle is one of the times at which a maker of needles shows their worth. The small hole is then polished and made smoother.
The larger the eye, the easier it is to thread the needle. And the rounder the eye, the less likely the thread is to break when threading. A regular eye prevents the thread from behaving irregularly and twisting as it is being sewn with. The eye and thread do of course touch, but because the inside has been polished smooth snapping of the thread is prevented.

The best shape for a needle is one that gradually and smoothly becomes thinner from the eye to the point. If the point becomes sharp too suddenly, the material will resist the needle's passage and risks being damaged. A needle that gradually becomes thinner almost eliminates the resistance of the material, enabling smooth stitching.

One important stage of making a needle is the polishing of the surface. Today the standard polishing method is a widthways polish, but Misuya needles use a lengthways polish. Widthways polishing can be effectively performed by rollers, but because it occurs perpendicular to the needle's passage through the material it increases resistance. In contrast, Chuubei's lengthways polishing produces lines so fine they cannot be seen with the naked eye, running in the same direction as the needle moves. These grooves act as guides when the needle passes through the fabric, enabling an even smoother passage. But if the grooves are large enough that they can be seen with the eye then the needle will not perform well. Nor will it perform well if the polishing is uneven. In order to achieve an even finish that does not distort the shape of the needle, a polish even on the scale of 0.001 millimeters is required. The polishing stage is a point where even long-experienced artisans nervously hold their breaths.

Even the final stage--the wrapping of the needles--occurs under the watchful eye of a human. Before wrapping, the quality of the forging and finish of each needle is checked one by one. A needle that is believed to have the potential to cause damage when used to sew is removed, so you can use each of the 25 needles contained in each pack with confidence. The wrapping is designed to protect the needles, so it features aluminum foil that prevents the buildup of humidity. It is also bears Chuubei's mark.