A rectangular-shaped copper wire and Edgewise Coil It's hollow. The same pipe.|Edgewise, rectangular wire, rectangular copper wire, for motor prototyping and mass production, URATANI ENGINEERING
Amazon.com: 925 Sterling Silver Rectangle Flat Wire Dead Soft Made in USA by CRAFT WIRE (2 x 1MM, 1 Foot)
Square and rectangular wire meshes | Haver & Boecker