The foundation of Double Works' products is the yarn "Raffi," which is spun from a blend of cotton waste. Unlike modern spinning methods, this yarn is made by artisans at a manufacturer in Osaka, who take great care in every step of the process.

Raffi is a blend of long staple cotton and cotton that is discarded during the yarn making process, making it a sustainable yarn made from recycled cotton waste.

Cotton waste contains many short fibers, and when made into yarn, it naturally creates an uneven texture.

When this yarn is used to knit sweatshirts and T-shirts, it creates a vintage-like uneven texture and a tasteful body reminiscent of the era when spinning technology was not yet developed.

The cotton air-spun yarn used in the body of the T-shirts in the Heavyweight series. This yarn is also called open-end yarn.

There are two main types of yarn: ring yarn and air-spun yarn. The difference lies in the spinning method: ring yarn is spun through a ring-shaped spinning frame, while air-spun yarn is spun by drawing the yarn together using a jet of air.

The surface of air-spun yarn is uneven, with a tight twist on the outside and a loose, scattered inner core. This allows the yarn to contain just the right amount of air and give it volume, and when made into fabric it has a dry, rough texture and a tough look.

Double Works selects an exceptionally thick air-spun yarn, count 8, which cannot be knitted on a regular circular knitting machine. To knit this thick air-spun yarn, they use a specially customized vintage circular knitting machine, the Standwheeler, and knit it luxuriously tightly. This results in a round-bodied jersey body with a very tough feel, as the extra-thick yarn is knitted tightly. However, because the air-spun yarn is voluminous, even when knitted tightly, it has a natural stretch, and while it has a heavy look and firmness, it is lighter and more flexible than it looks. It is also dry and pleasant to the touch, and you can enjoy the comfort of a round-bodied garment with no side seams.