Provided by Business Insider

Lululemon announced this week that it had recalled its black Luon yoga pants because they're too see-through. That particular item makes up 17 percent of all women's bottoms sold at the apparel retailer.

The pants are made of luon, a primary fabric found in most of Lululemon's performance wear products, from yoga pants to headbands.

Luon, which is trademarked by the brand, is 86 percent nylon and 14 percent Lycra. It's an important part of Lululemon's secret sauce.

So, what's so special about it? Why are customers willing to fork out $98 for a pair of luon yoga pants?

To start, the fabric is preshrunk, stretchy, and wicks away moisture from your body when you sweat.

The Lycra ensures that the fabric will never "stretch or bag out," while the nylon provides coverage.

Lululemon's Luon pants are made by Eclat Textile Co. in Taiwan, the same supplier that Lululemon has used for the past decade.

There are also a bunch of variations of luon that Lululemon uses, like brushed luon, reversible luon, and heathered luon. They're all trademarked too, and Lululemon assures that these variations "all have the same performance characteristics" as the regular version, though they may feel a bit different.

Lululemon is far from the only brand in performance-wear with its own fancy-named fabric. Trademarked fabrics are common in the athletic apparel industry.

Gap's Athleta calls the fabric for its yoga pants "Pilayo," which is a nylon/spandex blend. Under Armour's fabric, made from polyester/elastane, is called "StudioLux."

While it's still unclear what went wrong with Lululemon's transparent pants, the luon fabric will continue to be an important part of the brand. The company has blamed its Taiwanese supplier, but on Tuesday Eclat Textile Co. claimed the pants made for Lululemon were not "problematic," according to The Wall Street Journal.