In comparison, the current average price for a SINGER (r) 221 Featherweight is $350.00. SINGER (r) 222K, which is considerably rarer and more coveted, is presently selling for between $800 and $2,000. The SINGER (r) 221 was introduced in 1971 and discontinued in 1976. Featherweights are unique because they use one-piece needles that fold down into the hub when not in use. This design allows them to be more compact than two-piece versions of similar instruments. There are three main types of featherweights: single-string, double-string, and quadruple-string. The first type has one string across the neck and another one at the base of the guitar. The second type has two strings on each side of the body; these are usually played simultaneously. The third type has four strings, one on each corner of the fretboard. These are used by players who need multiple low notes. The SINGER 221 was released in 1971 and sold for $35 until its retirement six years later. It is now extremely rare and most available examples sell for well over $1000. A few decades later, SINGER released the SINGER 612, which was essentially the same instrument as the 221 but with some minor changes to fit in with SINGER's new "612" line of guitars.