This set of Tubes for the Apple iPod nano was released in 2005 along with the iPod nano Generation 1. Apple described the Tubes:
“Just slip your Apple iPod nano in from the bottom or through the screen window of one of these iPod nano tubes to add a splash of style and protection from scratches and bumps.”
Upon its release, Apple described the iPod nano as “the most fashionable and wearable iPod ever,” apparently because it featured a variety of wearable accessories. The Apple-designed accessories included a lanyard, an armband, and this “optional set of iPod nano Tubes in pink, purple, blue, green, and clear [that] offers fashionable protection in a sheer casing while enabling full operation of all functions including the Click Wheel.”
Each Tube is a “smooth, treated silicon design [that] resists dirt and stains.” The silicone is thinner over the Click Wheel and hold switch to allow operation of the iPod nano while it’s in the case.
Source: Apple