Low-profile insoles are made of carbon fiber, foam, and fabric/textile blends such as spandex, thermoplastic, and polyester.
Thickness varies by product: some listings call insoles 'ultra-thin' (one carbon-fiber option specifies 1.1 mm), while others are described more generally as 'thin' or 'low-profile' without a specific measurement.
Sizing ranges from specific fitted sizes to one-size-fits-most items. Many low-profile insoles include a trim-to-fit design so you can cut them to match your shoe size.
Ultra-thin carbon-fiber plates are intended to be placed under a shoe's existing removable insole so they sit discreetly inside most shoes without adding noticeable bulk.
Low-profile insoles are described as fitting easily into most shoes, including athletic shoes, work shoes, boots, casual footwear, and many tight-fitting shoes. Some options also work when shoes lack removable liners.
Many low-profile insoles are intentionally thin for tight or low-volume shoes; some are trim-to-fit, and product descriptions often note compatibility with tight-fitting footwear and with shoes that don't have removable insoles.