From the website: GRIPPY NOT STICKY – CAKES are recommended under snug tops as we don’t use any irritating adhesives to ensure super gentle coverage. CAKES gently grip the skin with your body’s natural heat GENTLE – We use 100% medical grade silicone & go through extensive skin safety and toxicity testing to ensure our girls (and their girls) have the most gentle coverage possible SUPER SEAMLESS – Our wide range of size options, all with a super- tapered edge, means no-show coverage